Okadaic acid inhibits phosphatidylethanolamine biosynthesis in rat hepatocytes

Okadaic acid, a specific inhibitor of protein phosphatase 1 and 2A, inhibited the synthesis of phosphatidylethanolamine via the CDPethanolamine pathway in isolated hepatocytes. Pulse-chase experiments and measurement of the enzyme activity demonstrated that the inhibition of phosphatidylethanolamine synthesis was not caused by an inhibition of CTP:phosphoethanolamine cytidylyltransferase, the putative regulatory enzyme. However, okadaic acid decreased the cellular diacylglycerol level to 30% of that in control cells. The data suggest that the availability of diacylglycerol limits phosphatidylethanolamine synthesis in okadaic acid-treated hepatocytes.