Inhibition of protein phosphatases activates glucose-6-phosphatase in isolated rat hepatocytes.

Incubation of hepatocytes in the presence of microcystin-LR, okadaic acid, calyculin A (inhibitors of protein phosphatases PP1 and PP2A) or microcystin-RR (a specific inhibitor of PP2A) activated glucose-6-phosphatase both in the supernatant and in intact or disrupted microsomes. Puromycin, an inhibitor of protein synthesis, totally suppressed this activating effect, suggesting the involvement of protein phosphatases in the regulation of glucose-6-phosphatase synthesis.