Studies on enzyme lysing yeast cell from Oerskovia sp. CK. V. Proteolytic enzyme from Oerskovia sp. CK lysing viable yeast cells.

Oerskovia sp. CK produced three types of yeast glucan hydrolases, one of them, F-L lysing viable yeast cells had proteolytic activity and considerable difference was observed between lytic and proteolytic activities in thermal stability. F-L was considered to be a single protein from following results. Both activities were influenced in parallel by acid treatment and inhibitors. The reaction rates of two substrates being added to the enzyme system were less than the sum of the rates of reactions measured separately. Both activities were detected in the same fraction by isoelectric focusing. On the evidence that F-L lost lytic activity by the heat treatment at 60°C for 15 min, we speculated that the enzyme underwent autolysis during heat treatment and binding site for polysaccharide was released, subsequently lost the lytic activity, since active site of F-L remained unaffectedly. These speculations were based on the following results. Difference in specific activity between native and treated F-L was not observed. The specific activity of heat treated F-L purified by gel filtration was 1.6 times more active than that of native F-L. Native F-L had a affinity for dextran but treated F-L lost it. F-L being treated in the presence of DFP was eluted at the same fraction where native F-L was eluted. Based on these results, a model for the yeast cell wall was proposed.