Medium chain fatty acids as specific substrates for diglyceride acyltransferase in cultured hepatocytes.

The fatty acyl substrate specificity for de novo diglyceride, triglyceride, and phospholipid synthesis in cultured hepatocytes was evaluated. The fatty acyl availability for diglyceride and phospholipid synthesis is restricted to fatty acids longer than myristic acid with octanoic and decanoic acids being excluded. On the other hand, octanoic and decanoic acids may serve as substrates for the diglyceride acyltransferase. Dodecanoic acid appears to occupy an intermediate position between medium and long chain fatty acids with respect to its availability as substrate for the esterification sites concerned. The availability of octanoate as a specific substrate for the diglyceride acyltransferase reaction in cultured hepatocytes enables the measurement of this activity in situ under conditions of overall triglyceride synthesis.