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)

N-(Cyanoacetyl)-L-phenylalanine (compound 1) and N-(3-chloropropionyl)-L-phenylalanine (compound 2) were studied as the first peptidic mechanism-based inactivators (suicide substrates) for the zinc protease carboxypeptidase A (CPA). A crucial deprotonation on the methylene alpha to the amide carbonyl of 1 and 2 has been suggested to lead to the transient formation of a ketenimine and an alpha, beta-unsaturated amide, respectively. Subsequently, it is proposed that these key intermediates trap an active site nucleophile, resulting in covalent modification of the protein. In competition with the inactivation process, the enzyme hydrolyzes the amide bonds in these molecules. Partition ratios of 1180 +/- 40 and 1680 +/- 60 were determined for 1 and 2, respectively. N-Acrolyl-L-phenylalanine (compound 4), the putative intermediate from 2, was independently studied to test the validity of the mechanistic scheme and was observed to be an active site-directed inactivator of CPA. A solvent deuterium isotope effect of 1.39 +/- 0.02 was noted for inactivation by 2 and one of 1.31 +/- 0.01 for its hydrolysis, in keeping with a proposed promoted water hydrolytic pathway for peptide hydrolysis by CPA (Christanson, D. W., and Lipscomb, W. N. (1989) Acc. Chem. Res. 22, 62-69). Details of the kinetic analysis and design concepts are discussed.
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PMID:Peptidic mechanism-based inactivators for carboxypeptidase A. 202 92

(R)-2-Benzyl-5-cyano-4-oxopentanoic acid (compound 4) was studied as a mechanism-based inactivator (suicide substrate) for the zinc protease carboxypeptidase A (CPA; peptidyl-L-amino-acid hydrolase, EC 3.4.17.1). This compound was designed rationally based on the knowledge of the active site topology and the reported stereospecific proton exchange on ketonic substrate analogue (R)-3-(p-methoxybenzoyl)-2-benzylpropanoic acid [Sugimoto, T. & Kaiser, E. T. (1978) J. Am. Chem. Soc. 100, 7750-7751] by CPA. It is suggested that enzymic deprotonation on the C-5 methylene moiety may result in the transient formation of a ketenimine as the key intermediate that partitions between turnover and enzyme inactivation. The enzyme inactivation exhibited pseudo-first-order kinetics, was irreversible, and could be fully prevented in the presence of the reversible inhibitor benzyl-succinate. The inactivation rate constant, kintact, was evaluated to be 0.083 +/- 0.003 min-1 and kcat was measured at 1.78 +/- 0.06 min-1. In turn, a partition ratio of 28 +/- 3 was calculated. The reversible inhibitor constant (Ki) was measured at 1.8 +/- 0.5 microM, indicative of a high affinity for compound 4 shown by CPA; however, Km for the turnover process was determined at 4.93 +/- 0.43 mM. Kinetic analysis and labeling by the radioactive form of the inactivator suggested that the stoichiometry for protein modification by compound 4 approaches a 1:1 ratio.
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PMID:Design of an effective mechanism-based inactivator for a zinc protease. 230 May 47

The turnover of neuronal histamine (HA) in nine brain regions and the spinal cord of the guinea pig and the mouse was estimated and the values obtained were compared with data previously obtained in rats. The size of the neuronal HA pool was determined from the decrease in HA content, as induced by (S)-alpha-fluoro-methylhistidine (alpha-FMH), a suicide inhibitor of histidine decarboxylase. The ratios of neuronal HA to the total differed with the brain region. Pargyline hydrochloride increased the tele-methylhistamine (t-MH) levels linearly up to 2 h after administration in both the guinea pig and the mouse whole brain. Regional differences in the turnover rate of neuronal HA, calculated from the pargyline-induced accumulation of t-MH, as well as in the size of the neuronal HA pool, were more marked in the mouse than in the guinea pig brain. The hypothalamus showed the highest rate in both species. There was a good correlation between the steady-state t-MH levels and the turnover rate in different brain regions. Neither the elevation of the t-MH levels by pargyline nor the reduction of HA by alpha-FMH was observed in the spinal cord, thereby suggesting that the HA present in this region is of mast cell origin. The half-life of neuronal HA in different brain regions was in the range of 13-38 min for the mouse and 24-37 min for the guinea pig, except for HA from the guinea pig hypothalamus, which had an extraordinarily long value of 87 min. These results suggest that there are species differences in the function of the brain histaminergic system.
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PMID:Histamine turnover in the brain of different mammalian species: implications for neuronal histamine half-life. 649 68