LIVER ACETYL COA CARBOXYLASE: THE DISSOCIATION-REASSOCIATION PROCESS AND ITS RELATION TO CATALYTIC ACTIVITY

Abstract

In a previous paper1 we reported that acetyl CoA carboxylase (E.C. 6.4.1.2) iso- lated in homogeneous form from chicken liver is an unusually large and asymmetric protein structure.The enzyme (in phosphate buffer, pH 7) has a molecular weight of about 8 million and a sedimentation coefficient of 53-58S.Its characteristic filamentous structure, revealed by electron microscopy, was easily dissociated into subunits with concomitant loss of enzymatic activity.Active filaments (70-100 A X up to 4000 A) were rapidly reconstituted by addition of isocitrate or other tri- and dicarboxylic acid anions.The present paper provides a more complete physical- chemical characterization of the protomeric and polymeric forms of acetyl CoA carboxylase, as well as an insight into the reversible dissociation-reassociation process and its relation to catalytic activity.