Isolation, purification and some chemical properties of an acid carboxypeptidase from Aspergillus niger var. Macrosporus.

Acid carboxypeptidase (peptidyl-L-amino-acid hydrolase, EC 3.4.16.1) was purified to a homogeneous state from the water extracts of Koji cultures of Aspergillus niger var. macrosporus. The molecular weight of the enzyme was determined to e 136 000 by sedimentation equilibrium method. The denatured specimen of the enzyme exhibited a molecular weight of 60 000 in the sedimentation equilibrium in 6 M guanidinium chloride, suggesting that the native enzyme is composed of two identical subunits. However, sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the enzyme showed an anomalous Ferguson plot, which may account for the inconsistent values of apparent molecular weights obtained by this method. The acid carboxypeptidase was found to be an acidic glycoprotein (pI, 4.1), composed of 955 amino acid, 140 mannose, 14 galactose and 30 glucosamine residues/molecule.