4'-Phosphopantetheine, a Cofactor Bound to Guanosine Triphosphate-dependent Acyl Coenzyme A Synthetase

A small molecular weight cofactor has been isolated from purified preparations of the guanosine triphosphate-spectic acyl coenzyme A synthetase of rat liver mitochondria.The synthetase enzyme becomes inactive on removal of the cofactor, and its characteristic activity is restored by adding back the cofactor to the complete system containing Coi-SH.In its active form, the cofactor possesses sulfhydryl groups, organic phosphate, and pantothenic acid in a ratio of 1: 1: 1.4'-Phosphopantetheine can replace the cofactor in all enzymic assays and shares with the cofactor all chemical and spectral characteristics.