Abstract
The purpose of the present experiment is to make clear the physiological properties of amylase of Phytophthora infestans. The stock culture H1 (RaceO) employed in the present investigation is the common race which was isolated from naturally-infected leaves of the variety Irish Cobbler at the Hokkaido National Agricultural Experiment Station. The base medium for the experiments was of the following composition, in gm/l: asparagine, 1. 3; KH2PO4, 0.5; K2HPO4, 0.5; MgSO4·7H2O, 0.5; CaCl2·2H2O, 0.5; glucose, 30.0; FeCl3, 0.001; and thiamine, 0.1ppm. The amylase formation of the fungus has been recognized both in the mycelium and in the culture filtrate, but its activity was weak. The optimum hydrogen-ion concentration for saccharogenic and dextriogenic activities of the enzyme was approximately pH 6.0-7.0 and the optimum temperature seems to lie at 40°C. Saccharogenic and dextriogenic activities of the enzyme in the mycelium were inactivated by heating the mycelial extract at pH 7.0 at 70°Cfor 15 minutes. On the other hand, when the extract of the mycelium was acidified to pH 3.5, held at 40°C for 15 minutes, and neutralized, the dextriogenic activity was almost inactivated, while saccharogenic activity remained in a small degree. From the above results, the writer concludes that the amylase of P. infestans is composed chiefly of α-amylase and contains a small amount of saccharifying enzyme.
