Secretion heterogeneity of lysosomal enzymes in Tetrahymena pyriformis.

A number of lysosomal enzymes are secreted from Tetrahymena pyriformis during growth and during starvation. The secretion is energy-dependent and kinetically different among hydrolases. On the basis of the secretion kinetics under starvation conditions, Tetrahymena hydrolases can be separated into three classes. The first group containing acid phosphatase, beta-glucosidase and alpha-galactosidase, are secreted slowly. Within this group about 4% of the initial cellular activity is released per hour. The second group of enzymes, including alpha-glucosidase, alpha-mannosidase and beta-galactosidase, exhibit moderate secretion (11-15% of the initial cellular activity per hour). The third group, N-acetyl-beta-hexosaminidase, has the highest rate of secretion (22% of the initial cellular activity per hour). N-Acetyl-beta-hexosaminidase shows a continuous increase in overall activity during starvation, which is completely blocked by adding cycloheximide; its secretion is also suppressed. Such involvement of enzyme biosynthesis was not seen in the first and second groups. Furthermore, treatment with weak bases caused inhibited secretion of differing degree among acid phosphatase (group I), alpha-glucosidase (group II) and N-acetyl-beta-hexosaminidase (group III).