Purification and properties of carbonic anhydrase B from porcine erythrocytes

Abstract

Carbonic anhydrase B (carbonate hydrolase EC 4.2.1.1) has been purified from porcine erythrocytes to at least 90% homogeneity, as measured by sedimentation velocity and electrophoresis at several pH values. The isoelectric point of the enzyme is at 7.30 and its molecular weight by short-column Yphantis sedimentation equilibrium is 30,375 ± 820. The partial specific volume calculated from the amino acid composition is 0.734 cc/g. The sedimentation constant, S 20, w 0, is 2.86 S. From these data, the frictional ratio, f f 0 , is 1.21. The enzyme contains approximately 1 mole of zinc per mole of protein, but no sulfur-containing amino acids or carbohydrate. The amino terminus is acetylated, and the carboxyl terminal sequence of amino acids has been determined by hydrazinolysis and carboxypeptidase A and B digestion to be lys-alaser-phe-COOH. This sequence is more similar to the corresponding sequence from the human enzyme than to that of the bovine.