Studies on palmitoyl-coenzyme A synthetase

Abstract

Palmitoyl-CoA synthetase of rat-liver microsomes was solubilized and purified. According to a hydroxamate-forming assay, a 5-6-fold purification was obtained. By an assay based on ATP formation from palmitoyl-AMP and pyrophosphate, no purification or even a fall in activity was found. Hydroxamate formation was dependent on the presence of CoA. The ATP-forming activity by microsomes was activated by preincubation with ATP and CoA by about 50%. The purified enzyme increased its activity 3-4-fold on preincubation. Incubation with ATP and palmitate, or with palmitoyl-AMP, caused a fall in ATP-forming capacity. This fall was prevented by the presence of CoA. The inactivated enzyme could be reactivated by incubation with ATP and CoA. The results are discussed in the light of the assumption of two forms of the enzyme, an active CoA-containing one and an inactive one.