Isolation of a membrane-associated Bacteroides gingivalis glycylprolyl protease

Abstract

A low-molecular-weight proteolytic enzyme was purified 47-fold from outer membranes of Bacteroides gingivalis ATCC 33277 by preparative polyacrylamide gel electrophoresis. The enzyme was present in all B. gingivalis strains tested but was not found in other species of black-pigmented Bacteroides. The molecular weight, determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, was 19,500 when the enzyme was heated to 100 degrees C in SDS before electrophoresis and 29,000 when it was mixed with SDS but not heated. The optimum pH, with azocasein as the substrate, was between 6.0 and 6.5. The activity was inhibited by phenylmethylsulfonyl fluoride, N-alpha-p-tosyl-L-lysine chloromethyl ketone, Hg2+, and various reducing agents. The enzyme was active against azocasein, azocoll, proline-rich protein from saliva, and the synthetic peptide glycyl-L-proline-p-nitroanilide. The enzyme did not degrade acid-soluble collagen nor did it hydrolyze various arginine- and lysine-containing synthetic substrates.