The Preliminary Characterization of the [beta]-Glucosidases in Achlya ambisexualis

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Abstract
A time course study of the growth of A. ambisexualis on a defined liquid medium revealed a positive correlation between glucose depletion from the medium and the accumulation and subsequent utilization of a cytoplasmic reserve polysaccharide. The enzyme .beta.-glucosidase was shown to increase in specific activity during growth, reaching a maximum concomitantly with a rapid decrease in cytoplasmic glucan. The involvement of .beta.-glucosidase in the utilization of this reserve polysaccharide was further shown by a 33% decrease in the glucan and a more than 2-fold increase in enzyme activity during sporulation. Isolated glucan was hydrolyzed in vitro to glucose by a crude enzyme preparation containing .beta.-glucosidase activity. Enzyme activity was found mainly in the soluble fraction of mycelial homogenates, but some activity was released by detergent from a membrane fraction. .beta.-Glucosidase activity was separated into 2 forms by gel filtration. These 2 species differ widely in size and substrate specificity. Both hydrolyzed p-nitrophenyl-.beta.-D-glucoside and the .beta.-1,6-linked disaccharide gentiobiose. The larger species showed the greatest activity against the .beta.-1,3-linked polymer laminarin and the .beta.-1,3-linked disaccharide laminaribiose. This affinity for laminarin and laminaribiose is consistent with the proposed role in the utilization of the cytoplasmic glucan which is a .beta.-1,3-linked polymer. A significant finding is the inability of this .beta.-glucosidase to hydrolyze cellobiose, thus indicating the lack of a functional role in a cellulase system.