PMID: 2111133May 1, 1990Paper

Substrate and inhibitor studies with human gastric aspartic proteinases

The Biochemical Journal
A BaxterJ E Pendlebury

Abstract

The separation of pepsin isoenzymes 1, 2, 3 and 5 (gastricsin) in human gastric juice was effected by chromatography on Mono Q ion-exchanger, and slow-moving proteinase was purified to homogeneity by using a modified procedure incorporating a novel affinity-chromatography step. The pH-activity profiles of these enzymes with mucus glycoprotein and basement-membrane substrates were determined; the profiles for pepsin 2 were noticeably different, and, in general, the pH optima for the hydrolysis of basement membrane were more acidic. Pepsin 1 expressed larger specificity constants (kcat./Km) than pepsin 3 with a series of synthetic peptide substrates, reflecting greater binding (smaller Km) by pepsin 1. Inhibitor studies at pH 1.7 and 4.5 with a series of P2-substituted lactoyl-pepstatins implied that valine at position P2 was optimal for inhibiting pepsins 1, 2 and 3 but detrimental for pepsin 5, whereas lysine at position P2 was tolerated well by pepsin 5 but not by pepsins 1, 2 and 3. The potency of lactoyl-pepstatin with lysine at position P2 did not increase as a function of pH. P2-substituted lactoyl-pepstatins failed to show any inhibitory selectivity among pepsins 1, 2 and 3.

Citations

May 1, 1995·Protein Science : a Publication of the Protein Society·M FujinagaM N James
Apr 1, 1995·Alimentary Pharmacology & Therapeutics·A J GawC C Jordan
Mar 1, 1993·Phytochemistry·J KervinenM Saarma
Sep 18, 2008·Journal of Agricultural and Food Chemistry·Mahesh VenkatachalamShridhar K Sathe

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