BIOTIN SUBUNITS OF ACETYL COA CARBOXYLASE AND PYRUVATE-CARBOXYLASE FROM A THERMOPHILIC BACILLUS

Two biotin-containing polypeptides of MW 140,000 and 22,000 were identified by gel electrophoresis in a sodium dodecyl sulfate-denatured extract of cells of a thermophilic Bacillus. These polypeptides can be separated from each other by gel filtration through Sepharose 6B or affinity chromatography on a Sepharose-avidin column. The larger polypeptide is renatured under appropriate conditions to yield enzymically active pyruvate carboxylase [EC 6.4.1.1]. Enzyme reconstitution experiments show that the smaller polypeptide is a component of acetyl CoA carboxylase [EC 6.4.1.2]. The biotin subunits of these 2 carboxylases are distinct from, and dissimilar to, each other. The demonstration that a pyruvate carboxylase-deficient mutant of the Bacillus contains the smaller, but not the larger, polypeptide corroborates this conclusion.