Role of α-galactosidase in osmotic regulation of Poterioochromonas malhamensis.

In Poterioochromonas malhamensis, osmotic regulation is mainly mediated by the formation and degradation of isofloridoside (α-galactosyl-1→1-glycerol). In cell homogenates an α-galactosidase can be demonstrated. About one hour after an increase in external osmotic pressure, the enzyme activity increases. external osmotic pressure, the enzyme activity increases. The increase is more pronounced with a higher osmotic change and appears to be due to de novo synthesis of the enzyme, as it can be prevented by preincubation with actinomycin D or actidion. When the increase in α-galactosidase was suppressed with actinomycin D, the in vivo degradation rate of isofloridoside was slowed down. These results indicate a function of the α-galactosidase in osmotic regulation.