Increasing activity of enzymes on pathway of triacylglycerol synthesis during adipose conversion of 3T3 cells.

When preadipose 3T3 cells pass from growing to resting state, they increase their rate of synthesis of triacylglycerol from precursors and convert to adipose cells. The behavior of two enzymes involved in the synthesis of triacylglycerol, glycerophosphate acyltransferase, and malic enzyme have been examined during the adipose conversion of 3T3-F442A in surface culture and in suspension culture stabilized with methylcellulose. Glycerophosphate acyltransferase activity rises sharply during the conversion and reaches a level of 80 times higher than that of another 3T3 subline in which practically no adipose conversion takes place (3T3-C2). The activity of malic enzyme also rises during the adipose conversion of 3T3-F442A and reaches a level of 15-fold higher than that of 3T3-C2. The activity of glycerophosphate acyltransferase responds more sharply than that of malic enzyme but the rise in activity is not sustained as long, so that the relative levels of the two enzymes change during the conversion. The adipose conversion appears to be the result of increases in the activity of the synthesizing enzymes, brought about by either of the two most physiological methods available for arresting the growth of cultured cells.