Apo-(acetyl-CoA carboxylase) completely free from the holoenzyme was prepared from biotin-deficient rat adipose tissue by using affinity chromatography. The apoenzyme does not aggregate under conditions favouring the transition of the holoenzyme to the polymeric form. Such transition is possible after the conversion of the apoenzyme into the holoenzyme in vitro, thus demonstrating the requirement of the prosthetic biotinyl group for enzyme activation.
