Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The crystal structures of zinc-free carboxypeptidase A (apocarboxypeptidase A) and the complex of glycyl-L-tyrosine with apocarboxypeptidase A are described and compared to the corresponding structures of the zinc-containing enzyme. Only small conformational changes in the zinc ligands accompany removal of the metal. Interactions between the tyrosine residue of glycyl-L-tyrosine and apocarboxypeptidase A are similar to those observed in the complex with the holoenzyme. However, in the absence of zinc, the carbonyl oxygen of the glycyl moiety now receives a hydrogen bond from the side chain of arginine-127. Although not as yet observed, a similar shift of the carbonyl oxygen of a susceptible bond from the zinc to arginine-127 could stabilize tetrahedral intermediates generated during the hydrolysis of substrates by carboxypeptidase.
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PMID:Crystallographic studies on apocarboxypeptidase A and the complex with glycyl-L-tyrosine. 658 Jun 31

The structure of the metalloenzyme carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.17.1) has been refined at 1.75 A by a restrained least-squares procedure to a conventional crystallographic R factor of 0.162. Significant results of the refined structure relative to the catalytic mechanism are described. In the native enzyme, the zinc coordination number is five (two imidazole N delta 1 nitrogens, the two carboxylate oxygens of glutamate-72, and a water molecule). In the complex (at 2.0-A resolution) of carboxypeptidase A with the dipeptide glycyl-L-tyrosine, however, the water ligand is replaced by both the carbonyl oxygen and the amino nitrogen of the dipeptide. The amino nitrogen also statistically occupies a second position near glutamate-270. Consequently, the coordination number of zinc may vary from five to six in carboxypeptidase A-substrate complexes. Implications of these results for the catalytic mechanism of carboxypeptidase A are discussed. In addition, three cis peptide bonds, none of which involves proline as the amino nitrogen donor, have been located fairly near the active site.
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PMID:Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution. 694 49

We compare the detailed binding modes of the 39-amino acid inhibitor from potatoes, glycyl-L-tyrosine, the ester analogue CH3OC6H4(CO)CH2CH(CO2(-))C6H5, and indole acetate to the exopeptidase carboxypeptidase A (EC 3.4.17.1). In the potato inhibitor, cleavage of the COOH-terminal glycine-39 leaves a new carboxylate anion of valine-38 having one oxygen on zinc and the other as a receptor of a hydrogen bond from tyrosine-248 of carboxypeptidase. Tyrosine-248 also receives a hydrogen bond from the amide proton of the originally penultimate peptide bond between tyrosine-37 and valine-38. This hydrogen bond suggests product stabilization which is available to peptides and depsipeptides but not to esters lacking an equivalent peptide bond (nonspecific esters). Also, this structure may represent the intermediate binding step for the uncleaved substrate as it moves along the binding subsites. In particular, this may be the binding mode for the substrate after association of the COOH-terminal region of the substrate with the residues at binding subsite S2 (tyrosine-198, phenylalanine-279, and arginine-71) and preceding entry into the catalytic site S1'. These stabilized complexes allow some understanding of the effect of indole acetate, shown here to bind in the pocket at S1', as a competitive inhibitor for esters (for which entry into S1' precedes the rate-determining catalytic step for hydrolysis) and as a noncompetitive inhibitor for peptides (for which entry into S1' is rate limiting). These results, including the binding mode of the ester analogue, are consistent with the original proposal from x-ray studies that both esters and peptides are cleaved with the carboxy terminus at S1', although not necessarily by the same chemical steps.
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PMID:Binding of ligands to the active site of carboxypeptidase A. 694 83

Semi-empirical calculations of conformational properties of acetyl-L-tyrosine, glycyl-L-tyrosine, acetyl-L-alanyl-L-tyrosine and acetyl-L-alanyl-L-alanyl-tyrosine and their noncovalent complexes with carboxypeptidase A (CPA) are presented. Each of these molecules binds in the active site of CPA by only one binding mode. The substrates are practically free of intramolecular tension. It is shown that the binding of an aromatic side chain of a C-terminal residue of substrate provides productive orientation of the susceptible peptide bond. The sterochemical aspects of the interactions of Tyr-248 and Glu-270 residues with the substrates are considered.
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PMID:[Theoretical conformational analysis of noinvalent carboxypeptidase A complexes with inhibitors and substrates]. 742 20

Crotamine, a basic, myonecrotic, histamine-releasing neurotoxin, was isolated from Crotalus durissus terrificus venom. Carboxypeptidase A was shown to be activated by crotamine when acting upon N-carbobenzoxyglycil-L-phenylalanine. However the activity of carboxypeptidase B upon the substrate hippuryl-L-arginine was not enhanced by this toxin. Teh basic histamine releasers protamine and compound 48/80 also activated carboxypeptidase A. These three agents activated both alpha-chymotrypsin when acting upon acetyl-L-tyrosine ethyl ester and also five snake venom phospholipase-like myotoxins acting upon egg yolk phosphatidylcholine. These findings suggest that the action of these agents during histamine release may involve the participation of specific intermediary hydrolases which, upon activation, would enhance their cytolytic effects on the sequence of events which lead to granule extrusion and histamine release from mast cells.
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PMID:The histamine releasers crotamine, protamine and compound 48/80 activate specific proteases and phospholipases A2. 930 35

The dipeptide glycyl-L-tyrosine (GY) can be either a substrate for carboxypeptidase A (CPA) or an inhibitor, depending on pH. In this work, we investigate the pH-dependent reactivity of this dipeptide in CPA-catalyzed hydrolysis using a combined quantum mechanical and molecular mechanical method. It is shown that the monoionic form of the dipeptide, prevalent at high pH, chelates the active site zinc ion, rendering the enzyme inactive. This inhibitory form is consistent with an earlier X-ray structure of the CPA-GY complex. On the other hand, the prevailing di-ionic form of the dipeptide at low pH was found to undergo hydrolysis via a nucleophilic mechanism, leading to an acyl-enzyme complex. The stability of this reaction intermediate is consistent with previous low-temperature solid-state NMR results. The calculated overall free-energy barrier of 20.1 kcal/mol is in excellent agreement with the experimental value of 19.9 kcal/mol.
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PMID:pH-Dependent reactivity for glycyl-L-tyrosine in carboxypeptidase-A-catalyzed hydrolysis. 2173 84

N,N'-diBoc-dityrosine (DBDY), which was synthesized by the oxidative C-C coupling of 2 N-Boc-L-tyrosine molecules, was conjugated with two isoniazid (INH) molecules. Due to the quenching effect of INH, DBDY-(INH)(2) lacks the fluorescence of DBDY. As such, it was tested for use in the detection of proteases by measuring fluorescence recovery. In this study, serine proteases (chymotrypsin, trypsin, subtilisin, and proteinase K), metalloproteases (thermolysin and carboxypeptidase A, dispase, and collagenase), aspartic proteases (pepsin and aspergillopepsin) and cysteine proteases (papain and chymopapain) were chosen. Reported optimum assay conditions were chosen for each enzyme. Only papain and chymopapain catalyzed the hydrolysis of DBDY-(INH)(2) and led to fluorescence recovery, possibly due to their extensive binding sites and the INH-mediated inhibition of metalloproteases and aspartic proteases.
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PMID:A dityrosine-based substrate for a protease assay: application for the selective assessment of papain and chymopapain activity. 2244 80


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