enzyme (enzyme), early in yeast in yeast is the meaning of that produced by the living cells in vivo as a biological catalyst. Most of the protein composition (minorities as RNA). In the body in very mild conditions, high efficiency, catalyze a variety of biochemical reactions, and promote the metabolism of organisms. Life activities of digestion, absorption, respiration, movement and reproduction are the enzymatic reaction. Enzyme is the basis for cell survival. Cell metabolism, including almost all the chemical reactions catalyzed by enzymes are carried out.
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About the source of the enzyme properties of the enzyme activity of enzymes found in the system naming convention naming the classification of enzymes called oxidoreductases (oxidoreductase) transfer of enzymes (transferases) hydrolases (hydrolases ) Lyases (lyases) isomerase (isomerases) synthesis enzymes (ligase) activity of the enzyme activity determination of enzyme activity of the factors regulating the catalytic role of the molecular basis of enzyme chemical composition of the enzyme activity of the enzyme Center for Molecular Structure and catalytic enzyme activity of plasminogen and plasminogen activator isozymes between allosteric enzyme modifying enzyme multi-enzyme complex and multi-enzyme system of multifunctional enzyme characteristics of enzymatic reactions catalyzed enzymatic reaction mechanism of enzyme reaction Application of enzymes in vivo why the missing enzyme in the human enzyme in the production of medical, life, meaning Profile
enzyme
mammalian cells to contain thousands of enzymes. They are either dissolved in the cytosol, or combined with a variety of membrane structure, or other structures located in a specific intracellular location. These enzymes collectively referred to as intracellular enzyme; In addition, there are some synthesis in the cell and then secreted into the extracellular enzyme ─ ─ extracellular enzyme. The ability of enzyme-catalyzed chemical reaction called the enzyme activity (or activity). Enzyme regulation can be controlled by many factors, so that the bio-physical changes to adapt to external conditions, life-sustaining activities. Without the participation of enzymes, metabolic rate can only be carried out very slowly, simply can not maintain life activities. Such as food must be the role of the enzyme to degrade into small molecules, can be through the intestinal wall, are organized in absorption and utilization. There pepsin in the stomach, the intestines have pancreas trypsin, chymotrypsin, lipase and amylase. Another example is the oxidation of animal food sources of energy,
red sole shoes, the oxidation process is catalyzed by the enzyme in a series completed. Enzyme catalysis in real terms: to reduce the activation energy of enzyme and inorganic chemical catalyst comparison: 1, the same point: 1) change the chemical reaction rate, its almost not consumption; 2) only exist in the chemical reaction catalyzed; 3) to accelerate the chemical reaction rate shorten the time to reach equilibrium, but does not change the balance point; 4) reduce the activation energy, the chemical reaction rate to accelerate. 5) will appear poisoning. 2 different points: the characteristics of the enzyme properties of an enzyme, high efficiency: catalytic efficiency higher than the inorganic catalyst, the reaction rate faster; 2, specificity: an enzyme that can only be one or a class of catalytic substrate, such as protease catalyzed hydrolysis of proteins into peptides only; 3, diversity: many kinds of enzymes, there are about 4000 kinds; 4, moderate resistance: refers to the chemical reactions catalyzed by enzymes are generally milder conditions in carried out. 5, regulation of activity could include: activator inhibitor and regulation, feedback inhibition regulation, covalent modification and allosteric regulation, and regulation. 6. Some of the enzyme catalytic and cofactor related. 7. Volatility, since most enzymes are proteins, which are high temperature, acid, alkali and other damage. In general, the optimal temperature of enzymes in animals 35 to 40 ℃, the optimum temperature of plant enzymes in the body in between 40-50 ℃; bacteria and fungi in the body of the enzyme optimum temperature vary greatly, and some enzymes optimum temperature of up to 70 ℃. Animals mostly in the 6.5-8.0 PH enzyme among the best, but there are exceptions, such as the optimum pepsin PH 1.5, PH optimum enzyme in plants mostly in between 4.5-6.5. These properties make the enzyme complex intracellular metabolism to the orderly conduct of the process, so that the normal metabolism and physiological function of adapting to each other. Ruoyin an enzyme defect caused by genetic defects, or other causes reduced enzyme activity, enzyme catalyzed reactions can lead to abnormal metabolic disorders that substance, or even disease. Therefore, the relationship between enzymes and medicine is very close. The source of enzyme called enzyme (Enzyme), in Greek, is found in yeast (zyme) in the mean. That is, in all kinds of yeast for every matter of life events was found, and was so named. At this point, Yeast enzyme does not mean,
louboutin sale, however: can only say that yeast is a natural body weight per unit volume of all living species and enzymes containing the most enzyme rich! Especially the beer yeast! Yeast is a single-cell microorganism, containing many enzymes, yeast with cells and tissues, and enzymes are proteins, usually a few thousands of proteins in yeast, so that the yeast contains enzymes, but not equal to the yeast enzyme. Enzyme found in 1773, Italian scientists 斯帕兰扎尼 (L. Spallanzani ,1729-1799) designed a clever experiment: the meat into small metal cages, and then let the hawk swallow. Over time he will be steamed out, found the pieces disappeared. So he concluded the gastric juice must contain the material to digest meat. But what, he did not know. In 1836, German scientists Schwann (T. Schwann ,1810-1882) extracted from the juice out of the digestion of protein substances. Unlock the mystery of his stomach. In 1926, the American scientist Sam sodium (JBSumner ,1887-1955) extracted from the beans seed the crystallization of urease and urease through chemical experiments confirmed that a protein. 30 years of the 20th century, scientists have a variety of enzymes extracted protein crystallization, and that is a kind of biological enzyme catalytic protein. 80 years of the 20th century, American scientists Cech (TRCech, 1947 -) and Altman (S. Altman, 1939 -) RNA is also found in a small number of biological catalysis. Enzyme had the habit of naming names and the system is usually named in two ways. Used to map the molecular structure of protein named
often based on two principles: 1. According to the catalytic substrate enzyme: hydrolysis of starch, such as enzyme called amylase, hydrolysis of proteins called proteases; sometimes with sources in order to distinguish between different sources of the same class of enzymes, such as pepsin, trypsin and so on. 2. According to the reaction type catalyzed by enzymes: catalytic hydrolysis of the substrate molecule known as enzymes, known as the reductase catalytic reduction reaction. Based on the above two principles are also integrated with the enzyme name or other features, such as succinic dehydrogenase, alkaline phosphatase, and so on. Used to name the relatively simple, learning to use longer, but the lack of systematic and is not reasonable, resulting in confusion of names of certain enzymes. Such as: intestinal kinase kinase and muscle, from the literal view, it seems like the role of different sources of the two enzymes, their mode of action is actually quite different. Another example: copper thiolase and acyl enzyme acetyl coenzyme A transfer is actually the same enzyme, but the names are completely different. In view of this newly discovered enzyme and increasing the development of a new enzyme to adapt to the situation, the International Association of Biochemistry Enzyme Commission recommended a system of enzymes and classification of naming scheme to determine the name of each enzyme systems and practices should be the name of . In addition, each enzyme has a fixed number. Enzyme system of naming naming system is based on the overall reaction catalyzed by enzyme based. Provides the name of each enzyme should be clearly written name and the catalytic properties of the substrate. If the enzymatic reaction from the reaction of two substrates, the substrate is required to list both of them use For example: alanine aminotransferase (habit name) written in the system name, it should be the substrate of the two Amino also be specified, so the name Because the system name are generally long, inconvenient to use, so the narrative can be used to name. According to the classification of the enzyme reaction catalyzed by enzymes different nature of the enzyme is divided into six categories: oxide reductase (oxidoreductase) to promote substrate oxidation or reduction. Transfer enzymes (transferases) between molecules of different substances to promote a certain chemical groups of the exchange or transfer. Hydrolytic enzymes (hydrolases) to promote hydrolysis. Lyases (lyases) catalyzed the double bond from the substrate molecule or off on a mission group Kaki reaction, namely, to promote a compound split into two compounds, or a compound synthesized by the two compounds. Isomerase (isomerases) to promote conversion of isomers of each other, the catalytic substrate molecule within the rearrangement. Synthesis enzymes (ligase) for each combination of the two molecules, while ATP molecules (or other nucleoside triphosphate) in the high-energy phosphate bond cleavage, which catalyzed the intermolecular association reaction. Biochemical Society in accordance with international harmonization of classification of enzymes released by the principle, on the basis of the above six categories, in each of these enzymes has been based on the role of the substrate or key features of groups, divided into several subgroups; order to accurate indication of the substrate or the nature of reactants, each divided into several sub-class group (Yaya class); each group contains a number of enzymes directly. For example: lactate dehydrogenase (EC1.1.1.27) catalyst following reaction:
Legend 1
The numbers are explained as follows:
catalytic reaction Legend 2
enzyme activity enzyme activity unit (U , active unit): unit of measurement of enzyme activity. 1961 International Conference enzyme provides: 1 unit of enzyme activity refers to specific conditions (25 ℃, the other for the optimum conditions), in 1min 1μmol internal energy conversion enzyme substrate, or into the substrate in the 1μmol For the amount of enzyme groups. Specific activity (specific activity): per minute per milligram of protein at 25 ℃ enzyme substrate into the micro moles. Specific activity of enzyme purity measurements. Activation energy (activation energy): the 1mol of all substrate molecules from the ground state into the energy needed to over-state. Active site (active site): enzymes containing the substrate binding site and participate in the substrate into the catalytic amino acid residues part of the product. Usually located in the active site of protein domains or protein subunits, or cracks between the parts of the surface depression, usually in three-dimensional space by the tight by some amino acids. Determination of initial velocity enzyme activity (initial velocity): the initial phase of enzymatic reaction products of the substrate into the speed, the concentration of the product at this stage is very low, the reverse reaction is negligible. Michaelis-Menten equation (Michaelis-Mentent equation): represents an initial rate of enzymatic reaction (υ) and substrate concentration ([s]) between the rate equation: υ = υmax [s] / (Km + [s]) m s constant (Michaelis constant): For a given reaction, the initial rate of enzymatic reaction (υ0) to reach maximum velocity (υmax) half of the substrate concentration. Catalytic constant (catalytic number) (Kcat): also known as conversions. Is a kinetic constant, the substrate is saturated in the next activity (or an activity area) catalyzes a reaction measurement of how fast. Catalytic constant equal to the maximum reaction rate divided by the total enzyme concentration (υmax / [E] total). Each activity or Mount parts of product per second into the amount of substrate (Mount [Seoul]). Double reciprocal plots (double-reciprocal plot): it is called Lineweaver_Burk mapping. The rate of enzymatic reaction of a reciprocal (1 / V) the reciprocal of the degree of substrate (1/LSF) of the mapping. x and y axis intercept representing the Michaelis constant and maximum velocity of the countdown. Lysozyme activity in regulating
competitive inhibition (competitive inhibition): by increasing the concentration of substrate inhibition can be reversed by an enzyme type. Competitive inhibitor is usually the normal substrate or ligands competing for the same protein binding sites. The inhibition of the increase of the Km υmax unchanged. Noncompetitive inhibition (noncompetitive inhibition): not only with the free enzyme inhibitor combination, but also with enzyme - substrate complex with an inhibition of enzymatic reactions. The inhibition of the Km remains unchanged υmax smaller. Anti-competitive inhibition (uncompetitive inhibition): only with the enzyme inhibitor - substrate complex but not with the free enzyme with a combination of inhibition of enzymatic reactions. This inhibition to both Km and υmax smaller but υmax / Km unchanged. A class of very complex protein material [enzyme; ferment], in promoting the reversible reaction (such as hydrolysis and oxidation) plays the same role as the catalyst. In many industrial processes are useful (such as fermentation, leather tanning and cheese production) enzyme is a colloidal organic material, made up of protein, bio-chemical changes to act as a catalyst that is apart from its role in fermentation: ~ the original . Factors that affect the enzyme activity Mitch Rees (Michaelis) and doors Tanzania (Menten) theory of intermediate products according to the enzymatic reaction rate equation is derived, that is m - the door formula (specific reference to the . Formula we can see the door from the m: enzymatic reaction rate by the enzyme concentration and substrate concentration, but also by temperature, pH,
louboutin shoes, and inhibitors of activator. (1) enzyme concentration on enzymatic reaction rate equation and the door from the meter and the enzymatic reaction rate enzyme concentration relationship diagram can be seen: the enzymatic reaction rate is proportional to the concentration of the enzyme molecule. When sufficient concentrations of substrate molecules, the enzyme molecules more faster conversion of substrate. But in fact, when the enzyme concentration is very high, not to maintain this relationship, the curve gradually moving gently. According to the analysis, which may be entrained high concentration of substrate due to entrainment has many of the inhibitors. (2) substrate concentration on enzymatic reaction rate in the biochemical reactions, if the concentration of enzyme is constant, the lower the initial concentration of substrate, the enzymatic reaction is proportional to the speed and substrate concentration, ie with the bottom the increase of concentration. When all the enzymes and intermediate products generated substrate binding, even if the increase of substrate concentration, the concentration of intermediate products does not increase, the enzymatic reaction rate is not increased. Can also be obtained, the concentration of the substrate under the same conditions, the enzymatic reaction rate is proportional to the initial concentration of the enzyme. The initial enzyme concentration, the enzymatic reaction rate to large.
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determination in practice, even if enzyme concentration is high enough, with the substrate concentration, enzyme reaction rate did not increase, or even suppressed. The reason: high concentrations of the substrate reduces the effective concentration of water, reducing the molecular diffusion, thereby reducing the enzymatic reaction rate. Excessive accumulation of the enzyme substrate molecule to produce an inactive intermediate, can not release the enzyme, which would reduce the speed of response. (3) temperature on the velocity of enzymatic reaction of various enzymes in the optimum temperature range,
christian louboutin sale, the strongest activity, the maximum enzymatic reaction rate. In the appropriate temperature range, the temperature is increased by 10 ℃, the corresponding enzymatic reaction speed can be increased by 1 ~ 2 times. Enzymes in different organisms the optimum temperature difference. For example, various enzymes in animal tissues optimum temperature 37 ~ 40 ℃; microbial enzymes in vivo the optimum temperature was 25 ~ 60 ℃, but there are exceptions, such as Aspergillus glucoamylase optimum temperature of 62 ~ 64 ℃; Bacillus megaterium, short Lactobacillus, Bacillus and other gas production of glucose isomerase, the optimum body temperature is 80 ℃; Bacillus subtilis amylase liquefied optimum temperature 85 ~ 94 ℃. Can be seen, some Bacillus higher thermal stability of the enzyme. Too high or too low a temperature will reduce the enzyme's catalytic efficiency, which reduce the enzymatic reaction rate. Optimum temperature below 60 ℃ of the enzyme, when the temperature reaches 60 ~ 80 ℃, most of the enzyme is destroyed, the occurrence of irreversible; when the temperature close to 100 ℃, complete loss of enzyme catalysis. So, in a fever, do not want to eat. (4) pH effect on the enzymatic reaction rate at the optimum pH range of enzyme showed activity greater than or less than the optimum pH, will reduce the activity. Mainly in two aspects: ① change the substrate molecule and the charged state of the enzyme molecule, thus affecting the combination of enzyme and substrate; ② too high or too low pH will affect the stability of the enzyme, and then the enzyme suffered irreversible damage. Most of the body pH, enzymes in which the environment closer to 7,
christian louboutin pumps, the catalytic effect is better. But the body of pepsin are suitable pH value of 1 to 2 environment, the optimum pH of trypsin in the 8 or so. (5) activators on enzymatic reaction rate can activate the enzyme as enzyme activator material. Activator, there are many different ① inorganic cations, such as sodium, potassium, copper ions, calcium ions; ② inorganic anions such as chloride, bromide, iodine ions, phosphate ions, sulfate ions; ③ organic compounds, such as vitamin C, cysteine, reduced glutathione. Many enzymes only when a certain presence of the appropriate activator, to demonstrate catalytic activity or enhanced catalytic activity, which called on the enzyme activation. Synthesized enzyme and some showed no activity by the state, the enzyme called plasminogen. It must be properly activated before the activation with activity. (6) inhibitors of the enzymatic reaction rate to decrease, inhibit or even undermine the activity of the substances called enzyme inhibitors. It can reduce the enzymatic reaction rate. Enzyme inhibitors heavy metal ions, carbon monoxide, hydrogen sulfide, hydrogen cyanide, fluoride, iodide, acetic acid, alkaloids, dyes, on the - chloro mercury benzoic acid, diisopropyl fluoro phosphate, EDTA, surface active agent. The inhibition of the enzymatic reaction can be divided into competitive inhibition and noncompetitive inhibition. Similar structure with the substrate material first to combine with the enzyme's active site, thereby reducing the enzymatic reaction rate, this effect is called competitive inhibition. Competitive inhibition is reversible inhibition, by increasing the concentration of substrate inhibition can be lifted eventually, restore enzyme activity. Similar structure with the substrate material as a competitive inhibitor. Inhibitor of the enzyme active site than the combination, the substrate can combine with the enzyme active site, but the enzyme does not show activity, this effect is called non-competitive inhibition. Non-competitive inhibition is not reversible, increase in substrate concentration does not relieve the inhibition of enzyme activity. Outside the enzyme active site inhibitor binding sites, known as non-competitive inhibitor. Some material can be used as an enzyme inhibitor, but also as an alternative enzyme activator. The catalytic acid - base catalysis (acid-base catalysis): proton transfer to accelerate the catalytic reaction. Covalent catalysis (covalent catalysis): a substrate or part of the substrate to form covalent bonds with the catalyst, and then transferred to the second substrate. Many enzyme-catalyzed by group transfer reactions are covalent manner. Catalytic mechanism of the catalytic mechanism and the same general chemical catalyst, is first and reactant (enzyme substrate) combined into a complex reaction by lowering the energy to improve the speed of chemical reaction, at a constant temperature, the chemical reaction system reactant molecules contained in each of energy although the difference is larger but the average low, this is the reaction of the initial state. S (substrate) → P (product) was able to carry out this reaction, because a considerable part of the S molecule has been activated to become activated (transition state) molecule, the more active molecule, the reaction rate faster. At a given temperature, the chemical reaction activation energy is to make a mole of a substance into all the elements required for activation of molecular energy (kcal). Enzyme (E) of the role is: being combined with S to form a new compound ES, ES activation state (transition state) than the chemical reaction without catalyst in the reactant molecules with the energy of activation is much lower. Further reaction ES P, while the release of E. S E with other molecules, and then repeat the cycle. Reduce the activation energy required for the reaction, so that the unit time to react with more molecules, the reaction rate can be accelerated. If no catalyst, the decomposition of hydrogen peroxide into water and oxygen reaction (2H2O2 → 2H2O + O2) required activation energy 18 kcal per mole (1 kcal = 4.187 J), hydrogen peroxide catalyzed this reaction When the activation energy of only 2 kcal per mole, the reaction rate increase of about 10 ^ 11 times. The molecular basis of enzyme activity of the chemical composition in accordance with the chemical composition of the enzyme activity can be divided into two simple classes of enzymes and enzyme combination. Pure enzyme, only amino acid peptide chain, with the addition of the enzyme protein peptide chains, as well as non-protein components, such as metal ions, iron porphyrin containing B vitamins or small molecule organic compounds. Part of the enzyme known as protein binding enzyme protein (apoenzyme), collectively referred to as non-protein part of the cofactor (cofactor), which together form the holoenzyme (holoenzyme); only have the catalytic activity of the whole enzyme, the enzyme activity if the two separate disappear . Non-protein parts such as porphyrin or compounds containing B vitamins and enzyme protein, if covalently linked as cofactor (prosthetic group), using dialysis or ultrafiltration can not be separated from them with the enzyme protein; the other hand two are non-covalently linked as coenzyme (coenzyme), this method can be used to separate the two. Table 4-1 for the metal ions and enzyme cofactor for some examples. Table 4-2 lists several vitamins containing coenzyme B (base) and its participation in the reaction. Of metal ions and enzyme function in many aspects, they may be components of the enzyme active center; some may stabilize the conformation of the enzyme on the work; some may be used as the enzyme and the substrate bridge connected. Coenzyme and prosthetic group as in the catalytic reaction of hydrogen (H + and e) or the carrier of certain chemical groups, hydrogen or from the chemical groups to pass the role. Many different types of enzymes, but the type of enzyme cofactors are not many, have been seen from Table 4-1 are several enzymes in some of the same metal ion as a cofactor example, the same situation is found in coenzyme and assistive base, such as 3 - phosphoglycerate dehydrogenase and lactate dehydrogenase are NAD + as a cofactor. The specificity of enzymatic reactions in the enzyme protein part of the decision, and the role of coenzyme and prosthetic group is involved in specific hydrogen during the reaction (H + and e) and some special chemical groups carrying. Enzyme active site of enzymes are biological macromolecules, molecular weight of at least 1 million or more, big up to millions. Enzyme catalysis depends on the enzyme molecules and the spatial structure of the primary structure intact. If the enzyme denaturation or subunit dissociation may result in loss of activity. One noteworthy issue is the reaction catalyzed by the enzyme substrate material that is (substrate), but most of them small sub-molecular weight material is smaller than the enzyme several orders of magnitude. Enzyme active center (active center) is only a small fraction of enzyme molecules, the majority of enzyme protein amino acid residues not in contact with the bottom. Enzyme active site composed of amino acid residues have different side chain functional groups, such as-NH2,-COOH,-SH,-OH and imidazole-based, and these enzyme molecules from different parts of the polypeptide chain. Some groups when combined with the effect of substrate binding groups (binding group) role, and some a catalyst in the catalytic reaction group (catalytic group) role. However, some groups play a role both in combination, but also play a role in catalysis, so often the active site of the functional groups collectively known as the required group (essential group). They coiled through the folding polypeptide chain to form an enzyme surface, with three-dimensional structure of the cavities or fissures, to accommodate access to bind to the substrate (Figure 4-1) and the catalytic substrate into a product of the region that called the enzyme active site. The enzyme active site functional groups other than the formation and maintenance in the conformation of the enzyme is also required, it must be called outside of the active center groups. Cofactor for enzymes required for cofactor is also part of the active center. Specificity of enzyme-catalyzed reaction depends on the enzyme active site is actually the combination group, the catalytic groups and their spatial structure. Enzyme catalytic activity and molecular structure of the relationship between the molecular structure of the enzyme is the basis of its amino acid sequence, which determines the spatial structure of the enzyme active center and the formation and enzymatic specificity. Such as the mammalian glyceraldehyde phosphate dehydrogenase amino acid sequence nearly identical, indicating that the primary structure is the same enzyme that catalyzes the same reaction basis. Another example is the digestive tract of chymotrypsin, trypsin and elastase hydrolysis of food proteins can be peptide bond, peptide bond hydrolysis but the three have their own specificity, chymotrypsin hydrolysis to provide aromatic amino acid residues containing carboxyl peptide bond, trypsin and other basic amino acid lysine residues to provide carboxyl peptide bond, and less flexible side chain hydrolysis and does not provide a charged amino acid residues carboxyl peptide bond. These three enzymes of amino acid sequence analysis showed that 40% of the amino acid sequence of the same, all the serine residues as the active center of enzyme groups, three enzymes in the serine residues are surrounded G1y-Asp-Ser-Gly-Pro sequence , X-ray diffraction studies suggest that these three enzymes have similar spatial structure, which they can be the basis of hydrolysis of peptide bonds. The hydrolysis of peptide bonds when they come from the enzyme specific substrate binding site on the amino acid composition due to slight differences. Figure shows the three enzyme substrate binding site have a bag-shaped structure, chymotrypsin that it can accommodate the aromatic or non-polar; trypsin bottom of the bag is slightly different one substituted amino acid residues Asp , so that it enhanced the negative charge, the Office of the positively charged lysine or a combination of fine acid residues favorable; elastase sides of pocket to valine and threonine residues are replaced, so there can only be with small side chains and groups without charge. That the catalytic specificity and the close relationship between the molecular structure of enzymes. Some of plasminogen and plasminogen activator in a variety of digestive enzymes such as protease precursor to an inactive form of synthesis and secretion, and then transported to specific parts of the body when necessary, by specific proteolytic enzymes into the active enzymes play a role. The catalytic activity of the enzyme is not a precursor called plasminogen (zymogen). Such as pepsinogen (pepsinogen), trypsinogen (trypsinogen) and chymotrypsinogen (chymotrypsinogen) and so on. Acting on a substance to make it into a pro active enzyme is known as the activation of plasminogen (zymogen andactivation of zymogen). The inactive zymogen into the active substances known as enzyme activator. Plasminogen activator for the activation of a certain specificity. For example, the synthesis of pancreatic cells chymotrypsin was originally composed of 245 amino acid residues of a single peptide chain, and 5 intramolecular disulfide bonds linked to the zymogen activation process shown in Figure 4-3. First by trypsin hydrolysis of arginine and 16 of 15 isoleucine peptide bond between residues, into a fully activated p-chymotrypsin catalytic activity, but this time the enzyme has not yet stable, self-chymotrypsin by p- catalysis, removal of two molecules with catalytic activity of dipeptidyl well as a stable structure of α-chymotrypsin. Under normal circumstances, the majority of plasma coagulation factors basically inactive zymogen form, and only when the damaged tissue or blood vessel lining, the inactive zymogen to the enzyme into the active, triggering a series cascade of enzymatic reactions that ultimately lead to soluble fibrinogen into fibrin stabilizing polymer, the quest for platelet clot formation. Plasminogen activator is the nature of specific peptide molecule plasminogen cut or remove part of the peptide bond after the enzyme active site is conducive to the formation of plasminogen activator have important physiological significance, on the one hand it guarantees that the cells themselves are not synthetic enzyme protease digestive damage, on the other hand make them in a specific physiological conditions and provisions of the site are activated and play its physiological role. Intimal damage, such as organizations or activated coagulation factor after; gastric chief cell pepsinogen secretion and pancreatic cells to produce the original of chymotrypsin, trypsinogen, elastase, respectively, the original activation of the stomach and small intestine into the corresponding active enzyme, to promote digestion of food proteins is an obvious example. Specific peptide bond in plasminogen activator caused widespread in vivo is an important organism in the way of regulating activity. If the abnormal activation of plasminogen will result in a range of diseases. The incidence of hemorrhagic pancreatitis is due to plasminogen into the small intestine without being activated when to activate the protease own pancreatic cells, leading to pancreatic bleeding and swelling. Isozyme isozyme (isoenzyme) concept: that the same isozyme is a class of catalytic chemical reaction, but the molecular structure of enzyme protein, physical and chemical properties and immunogenicity of a different class of enzymes. They exist in the same race or the same biological individuals of different organizations, even within the same organization, the same cells in different organelles. Isozyme has been no less than dozens of known species, such as hexokinase, lactate dehydrogenase, of which the lactate dehydrogenase (Lactic acid dehydrogenase, LDH) most clearly studied. Human and animal tissue in the spine, there are five elements in the form, they are following the same catalytic chemical reaction: the five isoenzymes are composed of four subunits. LDH in the skeletal muscle subunit (M) and myocardial-type (H type) of the points, two types of subunits of the amino acid composition is different in different proportions by the two subunits composed of a tetramer, there are five forms of LDH . The H4 (LDHl), H3M1 (LDH2), H2M2 (LDH3), H1M3 (LDH4) and M4 (LDH5). M, H subunits of different amino acid composition, which is determined by the different genes. Five LDH in the M, H ratio of different subunits to determine the difference between their physical and chemical properties. Electric ice usually can be separated into five kinds of LDH, LDH1 swimming fastest to positive, while the slowest mobility LDH5, several other in between, followed by LDH2, LDH3 and LDH4 (Figure 4-5 ) Figure 4-5 also shows a variety of different tissues contain different amount of LDH, myocardial and LDH2 LDHl amount to more, and skeletal muscle and liver LDH5 and LDH4 based. LDH isozymes in different tissues and organizations to use lactic acid difference in the physiological processes. LDH1 and LDH2 affinity of lactic acid, causing oxidation of pyruvate, lactate dehydrogenase, in favor of myocardial lactate oxidation to obtain energy from. LDH5 and LDH4 great affinity for pyruvate, with the role of pyruvate reduction to lactate, which made the muscle energy in the anaerobic glycolysis in the corresponding physiological process (see Chapter glucose metabolism). Lesions in the organization of these isoenzymes released into the blood, the distribution of isoenzymes in different tissues and organs, so there is a change of serum isozymes. Therefore, commonly used in clinical diagnosis of serum isoenzyme analysis disease (Figure 4-5). Allosteric enzyme allosteric enzyme (allosteric enzyme) is often a multisubunit quaternary structure of oligomeric enzymes, enzyme catalysis in addition to the active center, also known as catalytic sites (catalytic site) outside; there are allosteric site (allosteric site). The latter is a combination of allosteric agent (allesteric effector) position, when it is combined with the allosteric agent, the enzyme's molecular conformation changes will be minor, affecting the catalytic sites of the substrate affinity and catalytic efficiency. If the allosteric agent with the enzyme and substrate affinity or increased catalytic efficiency of the known allosteric activator (allostericactivator), otherwise the enzyme substrate affinity or catalytic efficiency of r is called allosteric inhibitors reduced (allostericinhibitor). Activity regulation by the allosteric effect of agents known as allosteric regulation (allosteric regulation) role. Allosteric enzyme catalytic sites and the allosteric sites can coexist in different parts of a subunit, but more in a different subunit, respectively. In the latter case, the subunit with catalytic sites of the catalytic subunit said, and with said allosteric regulatory subunit loci. Most of allosteric enzymes in metabolic pathways beginning, but allosteric enzyme allosteric agents are often some of the physiological role of small molecules and enzyme substrates or intermediate products of the metabolic pathways or end products. Therefore, the catalytic activity of allosteric enzymes by substrate concentration of intracellular metabolic intermediates or end products in the regulation of concentration. End product inhibition of the pathway of allosteric enzyme known as feedback inhibition (feedback inhibition). Once the cells that end products increase, as allosteric inhibitor of the enzyme in the metabolic pathway starting, adjust the speed of the metabolic pathways to meet the needs of cell physiology. Allosteric enzyme in cells on the regulation of metabolism play an important role. Therefore, allosteric enzyme, also known as regulatory enzymes. (Regulatory enzyme) that some enzymes require modifying enzymes in the body under the action of other enzymes, the molecular structure of the enzyme after modification with catalytic activity,
christian louboutin shoes, such as modifying enzymes enzyme (modification enzyme). Which covalent modification is common, such as the enzyme protein serine, threonine residues of functional groups-OH can be phosphorylated, this time accompanied by changes in covalent modification of production, it said covalent modification (covalent modification). Because of this modification lead to changes in activity known as covalent modification of enzyme regulation (covalent modification regulation). The body of the most common covalent modification of enzyme phosphorylation and dephosphorylation, in addition to the enzyme acetylation and deacetylation, uridine to uridine acidification and acidification of methylation and demethylation. Because covalent modification of quick response, it has a cascade effect amplified the body regulate metabolism is an important way. The first step reaction catalyzed glycogenolysis as glycogen phosphorylase activity and no activity in the presence of two forms, known as the active phosphorylase a, no activity as phosphorylase b, these two forms of interaction change is through enzyme phosphorylation and dephosphorylation process (see Chapter glucose) multi-enzyme complex and multi-enzyme system of the body together of some enzymes with each other to form a physical combination, the combination known as multi- enzyme complex (multienzyme complex). If the disintegration of the multi-enzyme complex, then lost the catalytic activity of the enzyme. To be part of multi-enzyme complex of the enzyme more or less, such as the catalytic reaction of oxidative decarboxylation of pyruvate pyruvate dehydrogenase multi-enzyme complex formed by the three enzymes, and in mitochondrial fatty acid β-oxidation in the multi-enzyme complex formed by the four enzymes. 1. 2. 3. So, now popular with the 3.
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