Pantothenate synthetase of Escherichia coli B. I. Physicochemical properties

Using a new apparatus for preparative polyacrylamide gel electrophoresis, pantothenate synthetase (D-pantoate: beta-alanine ligase (AMP-forming), [EC 6.3.2.1] was purified about 500-fold from Escherichia coli B. It was found to be homogeneous in analytical disc gel electrophoresis and sedimentation ultracentrifugation (so20, w=4.9). From sedimentation equilibrium ultracentrifugation, a molecular weight of 70,100 was obtained, which is in good agreement with the value obtained by the Sephadex G-150 gel filtration method (69,000); the diffusion constant was calculated to be 5.88X10(-7) cm2/sec. The minimum molecular weight calculated from the amino acid composition of this enzyme protein was 19,700, a value in reasonable accord with molecular weight of the enzyme subunit, 18,000, obtained by gel electrophoresis in the presence of sodium dodecylsulfate. The partial specific volume, v, was calculated to be 0.71 cm3/g. The enzyme had an amino-terminal glycyl residue and a Leu-Ala-Ser-OH sequence at the carboxyl end. Electrophoresis of the enzyme with carrier ampholine gave an isoelectric point of pH 4.6.