PMID: 6446Jun 10, 1976

Rat intestinal brush border membrane peptidases. II. Enzymatic properties, immunochemistry, and interactions with lectins of two different forms of the enzyme.

The Journal of Biological Chemistry
Y S KimJ A Nicholson

Abstract

The properties of two purified peptidases derived from the intestinal brush border membrane of the rat have been investigated. The pH optima, heat stabilities, substrate specificities, and metal ion requirements of the two enzymes and the effects of inhibitors on their activities were nearly identical. The isoenzymes catalyzed the hydrolysis of a wide range of peptides containing from 2 to 8 amino acid residues. The enzymes are aminopeptidases; no evidence for carboxypeptidase or endopeptidase activity was found. For hydrolysis, there appears to be an absolute requirement for an L-amino acid at the NH2-terminus of the peptide substrate. There was a similar but less absolute requirement for the penultimate NH2-terminal amino acid. Thus, although peptides of the type L-aminoacyl-L-proline, L-aminoacyl-L-prolyl-(L-amino acid)n, or L-aminoacyl-D-amino acid were not hydrolyzed, L-leucyl-beta-naphthylamide could be utilized as a substrate. The enzymes appeared to be metalloenzymes in that metal ion-chelating agents could inhibit their activities. Co2+ partially restored the activities lost by chelation. Immunodiffusion studies showed that the two enzymes were immunologically identical. The antipeptidase antisera were specific for the...Continue Reading

Related Concepts

Metazoa
Antibodies
Binding Sites
Cations, Divalent
Plasma Membrane
Metal Antagonists
Immunodiffusion Measurement
Hydrogen-Ion Concentration
Structure of Intestinal Gland
Alloenzymes

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