Acetyl Coenzyme A Carboxylase from Rat Liver

Acetyl-CoA carboxylase from rat liver has been purified to homogeneity as judged by gel electrophoresis, ultracentrifugation, and ultracentrifugation in the presence of 6 m guanidine hydrochloride. When the enzyme is subjected to gel electrophoresis in the presence of sodium dodecyl sulfate a sharp protein band is observed which has a molecular weight of about 215,000. In addition two sharp bands are observed which run closely together and which have molecular weights of about 118,000 and 125,000. Prolonged or repeated treatment of the heavy band with sodium dodecyl sulfate at an elevated temperature results in its conversion to the two light bands. It is concluded that the enzyme contains pairs of unlike subunits which remain associated to a considerable degree in sodium dodecyl sulfate at room temperature but which can be separated after more drastic treatment. Ultracentrifugation of the native enzyme yields an s20,w value of 45. Molecular weight determinations by sedimentation equilibrium in the presence of 6 m guanidine hydrochloride and mercaptoethanol yield a molecular weight for the subunits of the enzyme of 111,100. The amino acid composition, biotin content, and phosphate content of the enzyme are presented.