Hydrolytic Enzymes of Euglena gracilis: Characterization and Activity as a Function of Culture Age and Carbon Deprivation*†

Abstract

Optimal assay conditions are described for 8 hydrolases of E. gracilis var. bacillaris, SM-L1 (streptomycin-bleached) strain, 7 of which have an acid pH optimum. Acid phosphatase, .beta.-galactosidase, .beta.-glucosidase, .beta.-fucosidase, cathepsin D, RNase, DNase and an esterase are active in cell homogenates. Amylase has very low activity, and .beta.-glucuronidase, arylsulfatase, .beta., N-acetyl-glucosaminidase, .alpha.-fucosidase, and .alpha.- and .beta.-mannosidase are inactive. Hydrolase activity increases as a culture proceeds from the midexponential to the late stationary-phase of growth, being most pronounced in the case of .beta.-glucosidase. In cultures deprived of a utilizable C source, the specific activities of the hydrolases (per mg total protein or dry weight) increase. When expressed on a per cell basis, however, the activities of DNase decrease while those of .beta.-galactosidase, cathepsin D and RNase increase. The hydrolases appear to be involved in the adaptation of Euglena to the metabolic demands imposed by different conditions of growth.