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)

1. The process by which the egg-yolk protein precursor vitellogenin is biosynthesized, assembled and secreted by Xenopus laevis (South African clawed toad) liver was studied. It was previously shown in other laboratories that vitellogenin contains the two egg-yolk proteins lipovitellin (mol.wt. 140 000) and phosvitin (mol.wt. 35 000). 2. Evidence is presented which shows that Xenopus liver microsomal fractions synthesize precursors of vitellogenin. These precursors were solubilized from the membranes with detergent and analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. This analysis indicated that there is only one precursor polypeptide, and this has mol.wt. approx. 200 000 +/- 20 000. This demonstrates that the egg-yolk proteins are translated as part of this larger polypeptide. 3. Experiments also demonstrate the existence of a microsomal proteinase which is able to cleave the precursor into smaller fragments. The nature of these fragments provided some indirect evidence that phosvitin and lipovitellin light chains are situated together within the precursor molecule. 4. These precursor data fit in well with structural studies on serum vitellogenin, since it has been shown that the latter protein consists of two identical subunits each with a mobility on sodium dodecyl sulphate/polyacrylamide gels identical with that shown by the microsomal precursor. This indicates that both the intracellular precursor and subunit of vitellogenin have similar (but not necessarily identical) molecular weights. 5. It was also shown that trypsin or chymotrypsin can cleave the serum vitellogenin into leucine- and serine-rich fragments which resemble lipovitellin and phosvitin respectively. Attention is, however, drawn to the fact that the serine-rich fragment is not identical with phosvitin, since it contains eight times more leucine than that expected for the authentic phosvitin molecule [Penning (1976) Ph.D. Thesis, University of Southampton].
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PMID:Studies on the biosynthesis, assembly and secretion of vitellogenin, an oestrogen-induced multicomponent protein. 84 74

Prolonged incubation of 1-(2-chloroethyl)-3-([1-14C]cyclohexyl)-1-nitrosourea with chymotrypsin resulted in covalent modification and concomitant inactivation of chymotrypsin via degradation of the nitrosourea to form cyclohexyl isocyanate. Cyclohexyl isocyanate was shown to be an active-site-specific inactivator of chymotrypsin. A cyclohexyl isocyanate to enzyme molar ratio of 0.63 was required to produce 50% enzyme inactivation, thus demonstrating the high specificity of inactivation. At 2.38 X 10(-4) M chymotrypsin this near stoichiometric inactivation was not significantly affected by the presence of 1, 5, and 10 mM L-lysine. Degradation of an excess of 1-(2-chloroethyl)-3-([1-14C]-cyclohexyl)-1-nitrosourea in the presence of enzyme yielded 1.11 +/- 0.07 mol of covalently bound [14C]cyclohexyl moiety per mol of enzyme inactivated. Short-term incubation demonstrated that the nitrosourea neither inhibited nor protected the enzyme from cyclohexyl isocyanate inactivation. Treatment of chymotrypsin with less than stoichiometric amounts of cyclohexyl isocyanate or titration of the active-site serine with phenylmethanesulfonyl fluoride followed by in situ degradation of excess 1-(2-chloroethyl)-3-([1-14C]cyclohexyl)-1-nitrosourea resulted in a decreased amount of covalently bound 14C proportional to the extent of inactivation by these reagents prior to 14C labeling. These results strongly suggest that cyclohexyl isocyanate, whether added directly or generated by CCNU degradation, reacted almost exclusively with the active site of the enzyme. The extent of this inactivation indicates that 70% of the CCNU degraded in such a manner as to form cyclohexyl isocyanate.
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PMID:Active site specific inactivation of chymotrypsin by cyclohexyl isocyanate formed during degradation of the carcinostatic 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. 85 51

A phosphorylated polypeptide (E4) of molecular weight 5000-6000, has been isolated from bovine embryonic enamel by Bio-Gel P-10 gel filtration and DE-52 ion-exchange chromatography. The peptide contains three serine residues all of which are phosphorylated. All three O-phosphoserine residues are in glutamic acid-O-phosphoserine-tyrosine sequences that are distributed relatively evenly along the polypeptide chain. Although it was not possible to sequence the entire polypeptide chain directly by automatic peptide sequencing, a partial sequence and peptide map was constructed on the basis of the sequence and composition of peptides derived by cyanogen bromide, trypsin and chymotrypsin digestion. The presence of glutamic acid, tyrosine and leucine adjacent to and near the O-phosphoserine residues may be important in calcium binding and in mineralization.
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PMID:Isolation, characterization and partial amino acid sequence of a phosphorylated polypeptide (E4) from bovine embryonic dental enamel. 88 76

Two isoinhibitors (II and III-B) have been isolated from kidney bean (Phaseolus vulgaris L.) in a highly purified state. Both were active against trypsin and chymotrypsin to the same extent. Their amino acid composition is characterized by a high content of half-cystine, aspartic acid (or asparagine) and serine, by the absence of valine, methionine and tryptophan. Glycine and serine were N-terminal in II and III-B respectively. Both isoinhibitors have C-terminal leucine.
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PMID:[Isolation and properties of trypsin isoinhibitors from kidney beans]. 90 94

A search for the source of the residual esterase activity of crude lima bean protease inhibitor-binding anhydrochymotrypsin preparations was undertaken. The preparations were found to contain about 40% of protein that possesses 1% (kc/Km) to 12% (kc) of the esterase activity of alpha-chymotrypsin. The active protein was isolated by affinity chromatography on soybean trypsin inhibitor-Sepharose. It appears to be an anhydroenzyme or a mixture of a limited number of anhydroenzymes in which a serine other than the catalytically essential serine-195 of the native enzyme has been converted to dehydroalanine.
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PMID:Residual esterase activity of lima bean inhibitor-binding anhydrochymotrypsin preparations. 92 2

The statistical availability of tryptophan and tyrosine residues with one ring face fully exposed to solvent was examined for two serine proteases and their derivatives by investigating the formation of charge transfer (CT) complexes between the aromatic donor residues of the protein and the acceptor 1-methylnicotinamide chloride. The availability of the ring face of one of the two exposed tryptophan residues in trypsin has been previously shown to be pH dependent and to parallel the acid side of the pH-activity profile of the enzyme. The present results indicate that, in diisopropylphosphoryl-trypsin (DIP-trypsin), this residue [which was identified as Trp-215 in native trypsin (chymotrypsin numbering)] is locked in a relatively rigid, pH-independent conformation with one ring face rotated out toward the solvent. In the zymogen and DIP-zymogen, the ring face is essentially unavailable. Chymotrypsin, like trypsin, has a pH-depent tryptophan residue available for complexation with the CT acceptor, but unlike trypsin, the pH dependence is apparently associated with dimerization of the enzyme. These and other data suggest this residue is the same as in the homologous trypsin structure, i.e., Trp 215, and that the ring face is mostly buried in the zymogen. Comparison of the crystal structure models of chymotrypsin and chymotrypsinogen shows that, as the specificity pocket opens up from its collapsed structure upon zymogen activation, the ring face of Trp-215 moves out and rotates relative to the surface of the enzyme in such a fashion as to become more accessible to solvent. These observations are in accord with the present CT results and provide additional support for the assignment of changes in Trp-215 availability to parallel changes in the conformation of the specificity pocket of these serine proteases. The present investigation also shows that, although a tryptophan ring face is partly exposed in DIP-chymotrypsin, its statistical availability more closely resembles that of the zymogen than the native enzyme. The reverse appears to be true for DIP-trypsin, which suggests the possibility that the specificity pocket in DIP-chymotrypsin may be partially collapsed while the catalytic residues are frozen in the conformation of the acyl-enzyme.
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PMID:Flexibility in the specificity site of serine proteases. 94 68

The 5-dimethylaminonaphthalene-1-sulfonyl group was specifically introduced into the active site region of the serine proteinases: alpha-chymotrypsin, trypsin and subtilisin Carlsberg by the method of affinity-labeling. The resulting fluorescent derivatives were studied by a variety of fluorescence techniques and the results were correlated with structural data available on these enzymes from X-ray analysis. As model compounds for the Dns-proteinases, the absorption and fluorescence properties of Dns-amide and Dns-ethyl ester were studied in ethanol/water and p-dioxane/water mixtures. The fluorescence emission transtion energies and quantum yields were related to four commonly employed solvent-polarity scales. Best correlations for different solvents were obatined with the empirical "Z" and "Y" scales. From inspection of the fluorescence emission transition energies of the Dns group in the Dns-proteinases and comparision with the model compound studies it was possible to assign "Z" values for the apparent microenvironment polarities of the Dns group in the Dns-proteinases. The apparent polarities of the microenvironments of the Dns group in Dns-Ser 195-chymotrypsin (Dns-chymotrypsin (I)); (Dns-Phe-CH2)-His 57-chymotrypsin; (Dns-Lys-CH2)-His 46-trypsin; and Dns-Ser 221--subtilisin Carlsberg (Dns-subtilisin (I)) are in the range of 89.5-92.5 on the "Z" scale. The apparent microenvironment polarity of the Dns group in Dns-Ser 183-trypsin (Dns-trypsin (I)) appears to be below 76.7 on the "Z" scale. The Dns group in Dns-chymotrypsin (I) and (Dns-Phe-CH2)-His 57-chymotrypsin appears to be rigidly bound as evaluated by fluorescence polarization studies. The effect of 2H2O on the fluorescence emission quantum yields of Dns-amide and Dns-ethyl ester was examined. In both cases the ratios of quantum yields in 2H2O:ethanol (8:2) to quantum yields in H2O:ethanol (8:2) was about 1.8. The 2H2O effect upon the fluorescence emission quantum yields of the Dns group has been used to investigate solvent accessibility of this chromophore in the Dns-proteinases. Acessibility studies using 2H2O are very promising and have some definite advantages over other existing methods. Energy transfer between the Trp residues and the bound Dns group was investigated in the Dns-proteinases. The mean transfer distance calculated from the observed transfer efficiencies are 18.1 A, 19.7 A and 18.4 A for (Dns-Phe-CH2)-His 57-chymotrypsin, Dns-chymotrypsin (I) and (Dns-Lys-CH2)-His 46-trypsin, respectivly. From models built using X-ray crystallographic coordinates for the protein atoms, the mean distance of separation between the Trp residues and the bound Dns group for the same set of conjugates ar 18.6 A, 17.5 A and 17.5 A, respectively. Considering the inherent difficulties in energy transfer studies, the results are in excellent agreement with the X-ray data.
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PMID:Specific fluorescent derivatives of macromolecules. A fluorescence study of some specifically modified derivatives of chymotrypsin, trypsin and subtilisin. 95 53

Characterization of the cyanogen bromide (CNBr) fragments of the beta chain of human haptoglobin revealed five major fragments resulting from cleavage of four methionyl residues. The fragments were isolated by gel filtration in guanidine-HCl on Sepharose 6B and Bio-Gel P10 and P60. Compositional analyses of the five cyanogen bromide fragments accounted for 248-253 amino acid residues in agreement with the number of residues determined for the intact beta chain. Most of the carbohydrate was attached to CNBr II. Automated amino-terminal sequence analysis and carboxyl-terminal hydrolysis with carboxypeptidase of the haptoglobin beta chain and cyanogen bromide fragments identified 139 residues, or about 55% of the beta-chain molecule. The placement of the fragments within the beta-chain molecule was established by sequence analysis of whole beta chain and a plasmin cleavage fragment. The position of CNBr V was confirmed by the absence of homoserine or homoserine lactone. Cyanogen bromide reaction of intact haptoglobin 1-1 resulted in the isolation of a beta-chain fragment, CNBr III, covalently attached to the intact alpha1 chain by a single disulfide bond. The beta chain was shown to have primary structural similarities to the chymotrypsin family of serin eproteases. Partial sequence analysis of CNBr V established the region which is comparable to the serine-195 active-site region: /Asp-Thr-Cys-Tyr-Gly-Asp-Ala-Gly-Ser-Ala-Phe/ (residues 189-199, chymotrypsinogen A numbering). The active-site serine-195 is replaced by alanine; however, the specificity residue of the trypsin-like enzymes, Asp-189, is preserved. Several minor cyanogen bromide cleavage products were also identified in yields of up to 15%. These minor cleavage products give evidence that tryptophanyl residues in proteins, or glycoproteins, are also susceptible to cyanogen bromide cleavage.
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PMID:Characterization of the cyanogen bromide fragments of the beta chain of human haptoglobin. 99 9

The serine proteinases trypsin, chymotrypsin, elastase, and acrosin bind to the proflavin resin, the sulfhydryl proteinases ficin, bromelain, and papain are retarded by the resin, whereas most proteins and enzymes tested are not bound. Elution of the bound activities is accomplished NaCl or by variation from the pH optimum of the enzyme. Commercially available enzymes that are bound or retarded are easily further purified by the column. The acrosin activity of sperm acrosomal extracts is separated into bound and unbound activities. Acrosin is purified 120-fold from sperm acrosomal extracts in a single step, yielding a specific activity of 96.
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PMID:Fractionation of of proteolytic enzymes by affinity chromatography on sepharose aminocaproyl proflavin. 100 11

The sequences of amino acid residues at the amino and carboxyl terminus and around the reactive sites of the trypsin chymotrypsin inhibitor PCI 3 from the seeds of runner beans (Phaseolus coccineus L.) were estimated by aminopeptidase O and carbosypeptidase A degradation before and after enzymatical modification with trypsin or chymotrypsin. Beginning at the amino terminus the sequences are :Ser-Glu-Ala-Gly-Gln-...,...-Ile-Tyr-Lys-Ser-Gln-(Pro)-...with Lys-Ser as reactive site against trypsin, ...-Asp-Val-Ala-Leu-Ser-(Pro)-...with Leu-Ser as reactive site against alpha-chymotrypsin, and ...-Thr-Arg-Ala-Lys-Phe-Leu as C-terminus. The importance of the serine residue in the reactive sites concerning the specificity of inhibitors is discussed.
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PMID:[Trypsin and chymotrypsin inhibitors in leguminosae VII. Partial amino acid sequences of the trypsin chymotrypsin inhibitor PCI 3 from Phaseolus coccineus (author's transl)]. 100 24


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