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 effect of viscosity on the rate of catalysis of carboxypeptidase A has been tested. By use of the tripeptide carbobenzoxy-l-alanyl-l-alanyl-l-alanine [Z(L-Ala)3] as substrate, it was shown that most of the effect on the hydrolysis rate caused by the presence of 30 or 40% methanol or glycerol in aqueous solution can be ascribed to a contribution of viscosity to the catalytic rate constant, kcat. Arrhenius plots of kcat in 30 and 40% glycerol or methanol are linear and almost parallel. When the rate constants are "corrected" for the viscosity of various media, the difference between the various Arrhenius plots is considerably reduced; it vanishes, within experimental error, when the effect of the dielectric constant of the solutions is taken into account as well. It is proposed that the viscosity of the medium can influence the rate-limiting step of the enzymic reaction, which is the rate of transitions over the energy barrier preceding product formation. According to the suggested mechanism, the enzyme--substrate complex can overcome this energy barrier by viscosity-dependent structural fluctuations. The quantitative agreement between the theory and the experimental results suggests that (a) due to the temperature dependence of the viscosity of the solution, the potential energy barrier of the reaction is about 5 kcal/mol lower than the observed activation energy and (b) information about the structural flexibility of the complex can be obtained by kinetic measurements.
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PMID:Viscosity-dependent structural fluctuations in enzyme catalysis. 42 12

In porcine pancreatic secretion procarboxypeptidase A exists in two states: as a monomer and as a binary complex of a type hitherto not observed in the pancreatic secretions of other species. This complex is shown to contain 1 molecule of procarboxypeptidase A and 1 molecule of a proteolytic zymogen we have designated as zymogen E. The two subunits of the complex have been separated by gel filtration in a denaturing solvent and the products used for compositional and NH2-terminal sequence analysis. We also fractionated the mixture obtained on activation of the binary complex and isolated homogenous preparations of porcine carboxypeptidase A and the diisopropylphosphoryl derivative of the enzyme formed from zymogen E. Zymogen E has an Mr of about 26,000 and on activation produces an enzyme of essentially the same Mr with properties very similar to those of human pancreatic protease E. It catalyzes the esterolysis of acetyl-L-alanyl-L-analyl-L-alanine methyl ester, but is inert towards acetyl-L-tyrosine ethyl ester and is readily inactivated by diisopropylophosphorofluoridate. Zymogen E has an amino acid composition different from those of porcine chymotrypsinogen A, B, or C. Its NH2-terminal sequence shows homology with the NH2-terminal sequence of lungfish proelastase A; yet, like human protease E, porcine protease E has relatively very low activity on intact elastin.
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PMID:Identification of a binary complex of procarboxypeptidase A and a precursor of protease E in porcine pancreatic secretion. 67 Feb 12

Histamine is known to exert profound effects on the cardiovascular system in many mammals. Carnosine (beta-alanyl-L-histidine) is a dipeptide previously known to be present only in a few tissues. It is our hypothesis that carnosine serves as a non-mast cell reservoir for histidine, available for histamine synthesis during periods of physiologic stress. To validate this hypothesis, we demonstrated the existence of carnosine in multiple histamine-rich tissues in several mammalian species; documented a metabolic link between carnosine and histidine, histamine and 3-methylhistamine (a degradation product of histamine) in unstressed animals, and showed that tissue carnosine is decreased simultaneously with an increase in tissue histamine during stress.
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PMID:The presence and significance of carnosine in histamine-containing tissues of several mammalian species. 208 37

O-[[(1R)-[[N-(Phenylmethoxycarbonyl)-L-alanyl]amino]ethyl] hydroxyphosphinyl]-L-3-phenyllacetate [ZAAP(O)F], an analogue of (benzyloxycarbonyl)-Ala-Ala-Phe or (benzyloxycarbonyl)-Ala-Ala-phenyllactate, binds to carboxypeptidase A with great affinity (Ki = 3 pM). Similar phosphonates have been shown to be transition-state analogues of the CPA-catalyzed hydrolysis [Hanson, J. E., Kaplan, A. P., & Bartlett, P. A. (1989) Biochemistry 28, 6294-6305]. In the present study, the structure of the complex of this phosphonate with carboxypeptidase A has been determined by X-ray crystallography to a resolution of 2.0 A. The complex crystallizes in the space group P2(1)2(1)2(1) with cell dimensions a = 61.9 A, b = 67.2 A, and c = 76.2 A. The structure of the complex was solved by molecular replacement. Refinement of the structure against 20,776 unique reflections between 10.0 and 2.0 A yields a crystallographic residual of 0.193, including 140 water molecules. The two phosphinyl oxygens of the inhibitor bind to the active-site zinc at 2.2 A on the electrophilic (Arg-127) side and 3.1 A on the nucleophilic (Glu-270) side. Various features of the binding mode of this phosphonate inhibitor are consistent with the hypothesis that carboxypeptidase A catalyzed hydrolysis proceeds through a general-base mechanism in which the carbonyl carbon of the substrate is attacked by Zn-hydroxyl (or Zn-water). An unexpected feature of the bound inhibitor, the cis carbamoyl ester bond at the benzyloxycarbonyl linkage to alanine, allows the benzyloxycarbonyl phenyl ring of the inhibitor to interact favorably with Tyr-198. This complex structure is compared with previous structures of carboxypeptidase A, including the complexes with the potato inhibitor, a hydrated keto methylene substrate analogue, and a phosphonamidate inhibitor. Comparisons are also made with the complexes of thermolysin with some phosphonamidate inhibitors.
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PMID:Crystal structure of the complex of carboxypeptidase A with a strongly bound phosphonate in a new crystalline form: comparison with structures of other complexes. 238 84

Crystallographic analysis of the binding of mercaptoacetyl-L-valyl-L-tryptophan to thermolysin suggests that this inhibitor is hydrolyzed by the crystalline enzyme. The apparent product of hydrolysis, L-valyl-L-tryptophan (Val-Trp), occupies the S1'-S2' subsites of the active site, not the S1-S1' subsites as observed previously for the dipeptide L-alanyl-L-phenylalanine (Ala-Phe). The difference in binding of Val-Trp and Ala-Phe is consistent with the specificity requirements and preferences of thermolysin. The binding of Val-Trp illustrates the mode of interaction of one of the products of peptide hydrolysis. High resolution crystallographic refinement indicates that the valyl amino group makes three hydrogen bonds to the enzyme and to solvent and, in addition, is 2.8 A from the carboxylate of Glu-143. This is the first instance in which a direct interaction has been observed between Glu-143 and the scissile nitrogen. As such, the study directly supports the mechanism of action for thermolysin proposed by Hangauer et al. (Hangauer, D. G., Monzingo, A. F., and Matthews, B. W. (1984) Biochemistry 23, 5730-5741) and, by analogy, indirectly supports the similar mechanism proposed for carboxypeptidase A (Monzingo, A. F., and Matthews, B. W. (1984) Biochemistry 23, 5724-5729).
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PMID:The binding of L-valyl-L-tryptophan to crystalline thermolysin illustrates the mode of interaction of a product of peptide hydrolysis. 334 46

L-Leucinthiol, a synthetic derivative of mercaptoethylamine with a hydrophobic side chain, was recently reported to be a potent inhibitor of microsomal aminopeptidase. The structural features necessary for interaction of mercaptoamines with this enzyme have now been explored more systematically. Optimal binding requires a primary amine linked to the mercapto group via two carbon atoms. Only a substituent with L-configuration at the 1 position increased the affinity toward the enzyme. The high degree of specificity and other evidence suggest that the mode of binding of these inhibitors is similar to that of substrates. Comparison of leucinthiol with other amino compounds suggest that the mercapto group makes a much greater contribution to the binding than the hydrophobic side chain. L-Leucinthiol is fairly specific for aminopeptidase although some inhibition of thermolysin and carboxypeptidase A is observed.
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PMID:Structural requirements for specific inhibition of microsomal aminopeptidase by mercaptoamines. 400 71

The 22076-Mr Zn2+-containing D-alanyl-D-alanine-cleaving carboxypeptidase of Streptomyces abuls G effectively catalyses the transfer of the N alpha, N epsilon-diacetyl-L-lysyl-D-alanyl electrophilic group of the standard tripeptide substrate N alpha, N epsilon-diacetyl-L-lysyl-D-alanyl-D-alanine to water. It also performs a weak beta-lactamase activity, hydrolysing penicillin into penicilloate at a very low rate. This protein consists of 212 amino acid residues in a single polypeptide chain. The N terminus is partially blocked as a result of the cyclization of the dipeptide Asn-Gly into anhydroaspartylglycine imide. The protein has been fragmented by cyanogen bromide into five fragments whose sequences have been determined via appropriate subcleavages with various proteases. The ordering of the cyanogen bromide peptide fragments has been carried out (a) by submitting the S-carboxymethylated protein to complete tryptic digestion and labelling the methionine-containing peptides thus obtained with iodo[14C]-acetamide, and (b) by submitting to limited tryptic digestion the S-[2-(4'-pyridyl)ethyl]-cysteine protein whose amino groups have been blocked by reaction with exo-cis-3,6-endoxo-delta 4-tetrahydrophthalic anhydride prior to digestion. The protein contains six cysteine residues in the form of three disulfide bridges. No homology is found by comparing this peptidase with other Zn2+-containing enzymes (carboxypeptidase A, thermolysin, carbonic anhydrase B and alcohol dehydrogenase) and several completely or partially sequenced, serine-containing D-alanyl-D-alanine-cleaving peptidases and Zn2+/serine-containing beta-lactamases.
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PMID:The complete amino acid sequence of the Zn2+-containing D-alanyl-D-alanine-cleaving carboxypeptidase of streptomyces albus G. 682 89

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

The recently discovered native endomorphins play an important role in opioid analgesia, but their metabolic fate in the organism remains relatively little known. This paper describes the application of high-performance liquid chromatography combined with electrospray ionization mass spectrometry to identify the degradation products resulting from the incubation of endomorphins with proteolytic enzymes. The native endomorphin-1, H-Tyr-Pro-Trp-Phe-NH2 (1), and endomorphin-2, H-Tyr-Pro-Phe-Phe-NH2 (2), and an analog of endomorphin-2, H-Tyr-Pro-Phe-Phe-OH (3), were synthetized, and the levels of their resistance against carboxypeptidase A, carboxypeptidase Y, aminopeptidase M and proteinase A were determined. The patterns of peptide metabolites identified by this method indicated that carboxypeptidase Y first hydrolyzes the C-terminal amide group to a carboxy group, and then splits the peptides at the Trp3-Phe4 or Phe3-Phe4 bond. The remaining fragment peptides are stable against the enzymes investigated. Carboxypeptidase A degrades only analog 3 at the Phe3-Phe4 bond. Aminopeptidase M cleaves the peptides at the Pro2-Trp3 or Pro2-Phe3 bond. The C-terminal fragments hydrolyze further, giving amino acids and Phe-NH2-s while the N-terminal part displays a resistance to further aminopeptidase M digestion. Proteinase A exhibits a similar effect to carboxypeptidase Y: the C-terminal amide group is first converted to a carboxy group, and one amino acid is then split off from the C-terminal side.
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PMID:Liquid chromatographic study of the enzymatic degradation of endomorphins, with identification by electrospray ionization mass spectrometry. 1042 May 97

A novel angiotensin I-converting enzyme (ACE) inhibitory peptide (RMLGQTPTK; 9mer) from porcine skeletal troponin C was investigated for its inhibitory profile. This peptide was noncompetitive and as hydrophobic as the known ACE inhibitory peptides. Aminopeptidase M quickly hydrolyzed 9mer, resulting in production of MLGQTPTK and LGQTPTK with inhibitory activities similar to those of 9mer. The main hydrolysis product of 9mer with carboxypeptidase A and B was RMLGQTPT showing very weak activity. Most products derived from 9mer hydrolysis by ACE, aminopeptidase, or carboxypeptidase showed weak but definite ACE inhibitory activities. Thus, 9mer was estimated to be a wholly efficient inhibitor with these fragment peptides.
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PMID:Inhibitory profile of nonapeptide derived from porcine troponin C against angiotensin I-converting enzyme. 1496 29


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