Microsomal palmitoyl-coenzyme A synthetase from rat liver. Partial and exchange reactions

The partial and exchange reactions of long-chain fatty acid activation were determined by using purified microsomal long-chain fatty acyl-CoA synthetase (EC 6.2.1.3). No significant ATP formation from palmitoyl-AMP and PPi, nor palmitoyl-AMP-dependent CoA disappearance could be demonstrated. Similarly, no palmitate-dependent [32P2]PPi–ATP exchange was catalysed by the pure enzyme. The above partial and exchange reactions were, however, catalysed by the parent microsomal fraction at a rate similar to that of the overall reaction. The implications of these results are discussed.