THE PRODUCTION OF PROTEASE ACTIVITIES BY STREPTOCOCCUS-ORALIS STRAINSISOLATED FROM ENDOCARDITIS

Nine Streptococcus oralis strains isolated from cases of endocarditis (n=5) and from the normal oral flora (n=4) were examined for their abi lity to produce a number of protease activities measured using the fol lowing 7-amido-4-methylcoumarin (-AMC) linked fluorogenic substrates: BOC-leu-ser-thr-arg-AMC, gly-pro-AMC, CBZ-lys-AMC, arg-AMC and BOC-val -pro-arg-AMC, a synthetic substrate for thrombin. The influence of glu cose and porcine gastric mucin on their production was determined. The distribution of the protease activities between cell-associated and s upernatant was not significantly associated with the origin of the str ains. However, BOG-leu-ser-thr-arg-AMC and BOC-val-pro-arg-AMC hydroly sing activity was greater in the supernatant while the gly-pro-AMC, CB Z-lys-AMC and arg-AMC hydrolysing activity was more cell associated, i rrespective of whether the cells were grown in minimal media supplemen ted with either glucose or PGM. Inclusion of increasing concentrations of glucose in media containing a constant PGM concentration (0.25 per cent w/v) resulted in significant reductions in the supernatant prote ase activity hydrolysing BOC-leu-ser-thr-arg-AMC and BOC-val-pro-arg-A MC while the cell-associated activity hydrolysing CBZ-lys-AMC and arg- AMC increased and the hydrolysis of gly-pro-AMC was essentially unalte red. The response of S. oralis proteolytic activities to changes in me dia composition, including the inclusion of a model glycoprotein, PGM, was not predictable but indicated that strains from endocarditis and from the normal oral flora were indistinguishable. The production of p roteases in vivo may depend upon the level of fermentable carbohydrate s in the circulation but at low concentrations elevated levels of prot ease activity, including a thrombin-like activity, may be found within fibrin-platelet thrombi associated with endocarditis.