Effect of arginine modifying reagents on pigeon liver fatty acid synthetase: evidence for the presence of essential arginine residues at the beta-ketoacyl reductase and enoyl-CoA reductase domain.

Pigeon liver fatty acid synthetase was inactivated by arginine modifying reagent, phenylglyoxal and 2,3-butanedione. The inactivation of overall fatty acid synthetase was accompanied by the loss of beta-ketoacyl reductase and enoyl-CoA reductase activity. The inactivation followed a pseudo-first order kinetics and sum of the second order rate constants for the two reductase reactions equaled that for the synthetase reaction. Inactivation of all three activities was prevented by NADPH or its analogs 2',5'-ADP and 2'-AMP but not by the corresponding nucleotides containing the 5'-phosphate. These results suggest that binding of NADPH to fatty acid synthetase involves specific interaction of the 2'-phosphate with the guanidino group of arginine residues at the active site of the two reductases. pH-Dependent inactivation by phenylglyoxal indicated that a group with a pka 7.5 is involved in the loss of enzyme activity. Stoichiometric results showed that 4 out of 164 arginine residues per enzyme molecule were essential for the enzyme activity.

Role of fatty acid binding protein in the modulation of inhibitory effect of fatty acids on fatty acid synthase and ATP-citrate lyase in developing human brain.

Inhibition of the activities of fatty acid synthase and ATP-citrate lyase (ATP-CL) by fatty acids and their CoA esters has been studied. Purified fatty acid binding protein from human fetal brain reverses this inhibition. This protein also activates the enzyme when added alone. ATP-citrate lyase and fatty acid synthase activity gradually increased with the advancement of gestation showing a relationship between high demand of fatty acid synthesis in developing brain and supply of its precursors.