A SERINE PROTEINASE OF A FUNGUS ISOLATED FROM DRIED BONITO KATSUOBUSHI

A proteinase was purified from an extract of the koji culture of a str ain of Aspergillus sydowi, isolated from ''Katsuobushi'', in a homogen eous state by polyacrylamide gel electrophoresis by ammonium sulfate f ractionation, and Butyl-Toyopearl, DEAE-Toyopearl and Bio-Gel P-100 co lumn chromatographies. The molecular weight of the enzyme was calculat ed to be about 40,000. The optimum pH activity was 7.0-7.5 at 37 degre es C and the optimum temperature was 45 degrees C at pH 7.2 for casein olytic activity. The enzyme was stable between pH 3.5-8.0 and a temper ature of up to 45 degrees C. As the enzyme activity was completely inh ibited with phenylmethylsulfonylfluoride, this enzyme was a kind of se rine proteinase. The enzyme had a different substrate specificity from other fungal serine proteinases reported so far from the results of c leavage of proangiotensin and oxidized insulin B-chain.