Structural Relationship of Biotin-Containing Enzymes

Acetyl-CoA carboxylase from yeast was isolated in homogeneous form and compared in its properties with pyruvate carboxylase from yeast. Both enzymes have very similar sedimentation coefficients and molecular weights. Both enzymes are composed of four protomers. Acetyl-CoA carboxylase and pyruvate carboxylase split under identical conditions into a variety of aggregates; besides the protomer, dimeric, trimeric and polymeric forms are found. Patterns of the dissociated enzymes obtained by sedimentation in sucrose density gradients and by electrophoresis in polyacrylamide are almost identical. Within the limits of sensitivity of the immunochemical techniques used in this study no cross reaction could be observed between anti-acetyl-CoA carboxylase and pyruvate carboxylase. This indicates that the substructures catalyzing the ATP-dependent carboxylation of biotin, common to both enzymes are not based on identical primary structures. From these results it is proposed that the genes for acetyl-CoA carboxylase and pyruvate carboxylase may have been derived from a common ancestor.