CHARACTERIZATION OF PROTEOLYTIC ACTIVITIES OF RUMEN BACTERIAL ISOLATES FROM FORAGE-FED CATTLE

The proteolytic activities of eight strains of ruminal bacteria isolat ed from New Zealand cattle were characterized with respect to their ce llular location, response to proteinase inhibitors and hydrolysis of a rtificial proteinase substrates. The Streptococcus bovis strains had p redominantly cell-bound activity, which included a mixture of serine a nd cysteine-type proteinases which had high activity against leucine p -nitroanilide (LPNA). The Eubacterium strains had a mainly cell-associ ated activity with serine and metallo-type proteinases which showed hi gh activity against the chymotrypsin substrate, ni-succinyl alanine al anine phenylalanine proline p-nitroanilide (NSAAPPPNA) and some LPNA a ctivity. A Butyrivibrio strain, C211, had a cell-bound mixture of cyst eine and metallo-proteinase activities and strongly hydrolysed NSAAPPP NA and LPNA while the high activity Butyrivibrio-like strain, B316, ha d a cell-bound, mainly serine proteinase activity which strongly hydro lysed NSAAPPPNA. A Prevotella-like strain, C21a, had a mixture of cyst eine, serine and metallo-proteinase activities which were cell-bound a nd hydrolysed LPNA. The activities of these strains did not match thos e of the bacterial fraction of rumen fluid, which contained activities mainly of the cysteine type with specificity towards the substrate N- succinyl phenylalanine p-nitroanilide. The contribution of these strai ns to proteolysis in the rumen is discussed.