Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.1 (chymotrypsin)
10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In delta-chymotrypsin the reactivity of methionine-192 towards p-nitrophenacyl bromide is strongly reduced when the alpha-amino group of isoleucine-16 has been acetylated. Since acetylation of isoleucine-16 brings delta-chymotrypsin to a conformation similar to its alkaline one this suggests that methionine-192 should present an impaired reactivity in the alkaline conformation of the protein. It is indeed observed that its chemical reactivity as a function of pH depends on the ionization state of the alpha-amino group of isoleucine-16 (pKapp 9 at 15 degrees C) as does the structure of the enzyme. Reciprocally, after chemical reaction of methionine-192 with hydrogen peroxide, isoleucine-16 presents a slower rate of reaction with fluorescamine than when methionine-192 is free. As a result of methionine-192 oxidation the apparent pK of the alkaline transition is shifted from 9 to about 11 at 15 degrees C. This is reflected in the disappearance of the lag phase previously observed for the initial activity of the enzyme when it is incubated at alkaline pH [Eur. J. Biochem. (1973) 39,293-300]. The absence of chemical reactivity of methionine-192 in the alkaline state of the enzyme is confirmed by the appearance of a lag phase in the reaction of the protein with iodoacetate after an incubation at alkaline pH. Such a lag phase does not appear when this incubation is carried out at neutral pH. Since this lag phase is similar to that which shows up in the activity during the isomerization of the enzyme from its alkaline to its neutral state, the present data are interpreted as implying a concerted movement of isoleucine-16 and methionine-192 during this isomerization process. They also indicate that in the alkaline form of the enzyme methionine-192 has moved back into the interior of the protein. Since the spectroscopic properties of the zymogen and of the high-pH form of the enzyme are similar they suggest that methionine-192 occupies in the alkaline conformation of the enzyme a similar position as it does in the zymogen.
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PMID:The conformational oscillation of delta-chymotrypsin involvement of methionine-192. 0 Dec 47

The modification of alpha-chymotrysin with phenacyl bromide has been reinvestigated over a wide pH range. Evidence is presented that indicates that the nature of the phenacyl-modified enzymes prepared by this reaction is dependent upon the pH of the reaction medium. The phenacyl alpha-chymotrypsin produced at low pH is most probably the Met-192 phenacylsulfonium salt, as proposed earlier, since it readily undergoes dealkylation using 2-mercaptoethanol. However, the phenacyl-enzyme prepared at neutral pH possesses a much reduced enzymatic activity and does not react with 2-mercaptoethanol to regenerate native alpha-chymotrypsin. In addition, incubation of the Met-192 phenacyl sulfonium enzyme at neutral pH causes a smooth irreversible change to the new phenacyl-enzyme as monitored by changes in enzymatic activity, susceptibility to dealkylation using 2-mercaptoethanol, and ultraviolet difference absorption spectral properties. The stoichiometries of both the low and neutral pH modification reactions have been determined, using [carbonyl-14C]phyenacyl bromide, to be 1 phenacyl group/enzyme molecule. In efforts to obtain information about the nature and mechanism of formation of the phenacyl alpha-chymotrypsin produced at neutral pH, alkylation reactions of modified alpha-chymotrypsins produced by His-57 functionalization with tosylphenylalanine chloromethyl ketone and by Met-192 oxidation to the sulfoxide have been investigated. The combined results of these studies have been initially interpreted in terms of a neutral pH, phenacyl bromide modification resulting in formation of a new modified enzyme via the Met-192 sulfonium salt.
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PMID:Reinvestigation of the phenacyl bromide modification of alpha-chymotrypsin. 0 93

Soybean Bowman-Birk inhibitor, a double-headed inhibitor of trypsin and alpha-chymotrypsin, was treated with cyanogen bromide and then pepsin to yield two inhibitory active fragments. Structural investigation showed that one of the fragments was derived from the trypsin inhibitory domain and the other from the chymotrypsin inhibitory domain of the inhibitor. In contrast to the unusual stability of the native inhibitor, the separated domains were less stable and could be inactivated with excess proteinases. These results suggest that the legume double-headed inhibitors acquired their unusual stability by duplicating an ancestral single-headed structure.
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PMID:Studies on soybean trypsin inhibitors. XIII. Preparation and characterization of active fragments from Bowman-Birk proteinase inhibitor. 2 70

A reinvestigation of the modification reactions of alpha-chymotrypsin with phenacyl bromide was carried out. Results conclusively demonstrate that the chemically and physically different modified enzymes prepared at pH 4 and at pH 7 both contain the phenacyl group at methionine-192 in the sulphonium salt form. Evidence to suppoort this conclusion derives from 13C nuclear-magnetic-resonance spectroscopic observations on [methylene-13C]phenacyl-enriched enzymes. More conclusively, the methionine-192-containing C-chain, derived by performic acid oxidative cleavage of radioactively-labelled enzyme prepared at pH 7, was shown to contain the phenacyl moiety and to undergo dealkylation by 2-mercaptoethanol with loss of this moiety. In addition, thermolytic cleavage of the high-pH enzyme results in fragmentation of the polypeptide chain in a fashion analogous to model reactions of phenacylmethionyl dipeptides and other methionine-192 sulphonium salts. A rationalization of the unusual nature of the high-pH phenacyl-modified enzyme based on the irreversible formation of stable conformation in which the phenacyl moiety is rigidly located in interior regions of the enzyme is presented and discussed.
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PMID:Evidence for a pH-dependent irreversible formation of a stable conformation of phenacyl-alpha-chymotrypsin. 2 56

The amino acid sequence of staphylococcal protease has been determined by analysis of tryptic peptides obtained from cyanogen bromide fragments. Selected peptides obtained from digests with staphylococcal protease, thermolysin, and chymotrypsin provided the information necessary to align the tryptic peptides and the cyanogen bromide fragments. The protease is a single polypeptide chain of some 250 amino acids and is devoid of sulfhydryl groups. The COOH-terminal tryptic peptide of of the protease molecule contains some 43 residues, most of which are aspartic acids, asparagines, and prolines. The amino acid sequence of this peptide was not determined. The primary structure near the active serine residue indicates that staphylococcal protease is related to the pancreatic serine proteases. However, it has little or no additional sequence homologies with these enzymes except for the regions near histidine-50 and aspartic acid - 91. These regions have striking similarities with the corresponding regions of protease B and the trypsin-like enzyme of Streptomyces griseus.
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PMID:The primary structure of staphylococcal protease. 9 22

The primary structure of the human plasmin B-chain has been determined. It consists of 230 residues divided in three cyanogen bromide fragments: The amino-terminal 24 residues, the carboxy-terminal three residues and the middle 203 residues. Sequence detemination was performed on the tryptic and the chymotryptic peptides obtained from the main cyanogen bromide fragment of this chain. Owing to similarities between some of the overlapping chymotryptic peptides, two different sequences were possible from these results. However, since the homologies with the pancreatic serine proteases and also the B-chains of thrombin and factor XA are pronounced, the arrangement still could be settled. By peptic digestion of partially reduced and S-carboxymethylated B-chain it was shown that there are two interchain disulphide bridges, which connect the A and B-chains of plasmin, involving Cys-5 and Cys-105 from the B-chain. The intrachain disulphides in the B-chain seem to be situated exactly as in chymotrypsin as partly judged from homologies.
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PMID:Primary structure of the B-chain of human plasmin. 14 9

The amino-acid sequence of tyrosinase from Neurospora crassa (monophenol,dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) is reported. This copper-containing oxidase consists of a single polypeptide chain of 407 amino acids. The primary structure was determined by automated and manual sequence analysis on fragments produced by cleavage with cyanogen bromide and on peptides obtained by digestion with trypsin, pepsin, thermolysin, or chymotrypsin. The amino terminus of the protein is acetylated and the single cysteinyl residue 96 is covalently linked via a thioether bridge to histidyl residue 94. The formation and the possible role of this unusual structure in Neurospora tyrosinase is discussed. Dye-sensitized photooxidation of apotyrosinase and active-site-directed inactivation of the native enzyme indicate the possible involvement of histidyl residues 188, 192, 289, and 305 or 306 as ligands to the active-site copper as well as in the catalytic mechanism of this monooxygenase.
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PMID:Amino acid sequence of tyrosinase from Neurospora crassa. 15 Dec 79

Although the tripeptides Glu-O-Phosphoserine-Tyr and Glu-O-Phosphoserine-Leu have been identified in embryonic bovine enamel proteins, 1, 2 the issue of whether both sequences occur in each of the phosphopeptides, or whether certain sequences occur in specific peptides only, has recently been resolved by isolating homogeneous samples of E33 and E44. All three of the Ser residues of both peptides are phosphorylated. All three in E3 are in the sequence Glu-O-Phosphoserine-Leu, and all three in E4 are in the sequence Glu-O-Phosphoserine-Tyr. It was not possible to sequence either of the polypeptide chains directly by automatic peptide sequencing. However, a partial sequence of E4 was constructed from data derived from peptides isolated after cyanogen bromide, trypsin and chymotrypsin digestions. The presence of Glu, Tyr and Leu adjacent to and near the O-Phosphoserine [Ser(L)] residues and the 2 degrees, 3 degrees and higher ordered structures of the enamel phosphopeptides may be important in calcium binding and mineralization.
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PMID:Phosphopeptides of enamel matrix. 28 20

The amino acid sequence of the L-arabinose-binding protein of Escherichia coli B/r was determined by sequenator analyses of reduced and S-pyridylethylated L-arabinose-binding protein and fragments derived by chemical and enzymatic cleavage of the native protein. The fragments were the products of cleavage by cyanogen bromide. BNPS-skatole, hydroxylamine, mild acid hydrolysis, limited trypsin digestion, chymotrypsin subdigestion, and subdigestion with Staphylococcus aureus protease V8. The COOH-terminal sequence was determined using bovine carboxypeptidases A and B and amino acid analyses. The L-arabinose-binding protein was determined to contain 306 amino acid residues, the sequence of which is presented below.
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PMID:Amino acid sequence of the L-arabinose-binding protein from Escherichia coli B/r. 32 84

The complete amino acid sequence of the mangano superoxide dismutase from Escherichia coli B has been deduced through characterization of peptides from cyanogen bromide, bromonitrophenylsulfenyl skatole, citraconylated tryptic, and succinylated tryptic digests of the intact polypeptide chain and through subfragmentation of selected peptides with chymotrypsin, thermolysin, trypsin, and Staphylococcus aureus V8 extracellular protease. No significant homology is detected on comparison with the sequence of the copper- and zinc-containing superoxide dismutase from bovine erythrocytes, indicating that the manganese-iron and the copper-zinc classes of dismutases arose from independent evolutionary ancestors, a proposal previously based solely on enzymological and NH2-terminal sequence data. The amino acid sequence listed below corresponds to a molecular weight of 22,900 and appears to be identical in each subunit polypeptide of the native enzyme dimer. formula: (see text).
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PMID:The amino acid sequence of mangano superoxide dismutase from Escherichia coli B. 36 8


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