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

SYNOPSIS. Optimal assay conditions are described for 8 hydrolases of Euglena gracilis var. bacillaris, SM‐L1 (streptomycinbleached) strain, 7 of which have an acid pH‐optimum. Acid phosphatase, β‐galactosidase, β‐glucosidase, β‐fucosidase, cathepsin D, RNase, DNase, and an esterase are active in cell homogenates. Amylase has very low activity, and β‐glucuronidase, arylsulfatase, β, N‐acetyl‐glucosaminidase, α‐fucosidase, and α‐ and β‐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 β‐glucosidase. In cultures deprived of a utilizable carbon 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 β‐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.