Possible physiological role of myocardial fatty acid binding protein in phospholipid biosynthesis.

Accumulation of free fatty acids and their esters resulting from the degradation of membrane phospholipids is one of the major causes for the myocardial dysfunction during ischemia and reperfusion. In this communication, we have studied the possible physiological role played by fatty acid binding protein (FABP) in stimulating key enzymes involved in phospholipid biosynthesis. Purified rat heart FABP bound a maximum of either 2 mol of [1- 14C]palmitoyl coenzyme A (CoA), oleoyl CoA, or oleic acid per mol of FABP as observed by Scatchard analysis. FABP caused a threefold increase in the incorporation of [1- 14C]palmitoyl CoA into phosphatidic acid as compared to only a 1.5-fold increase by bovine serum albumin (BSA). Myocardial FABP also enhanced acyl CoA monoacylglycerophosphorylcholine acyl transferase minimally at a substrate concentration (greater than 200 microM), the activity of this enzyme was enhanced 4.5- and 2-fold by FABP and BSA, respectively. The maximum stimulation of the enzyme activity took place at the fatty acyl CoA concentration where inhibition of the enzyme activity is usually observed due to the surfactive property of acyl CoAs. These results thus indicate that under abnormal pathophysiological conditions such as ischemia, when acyl CoA concentration increases, FABP may protect acyl CoA monoacylglycerophosphorylcholine acyl transferase as well as stimulate glycerophosphate acyl transferase to limit the loss of membrane phospholipids, suggesting a possible role of FABP in phospholipid biosynthesis.