THE AMINO-ACID-SEQUENCES OF CARBOXYPEPTIDASE-I AND CARBOXYPEPTIDASE-II FROM ASPERGILLUS-NIGER AND THEIR STABILITY IN THE PRESENCE OF DIVALENT-CATIONS

The amino acid sequences of serine carboxypeptidase I (CPD-I) and II ( CPD-II), respectively, from Aspergillus niger have been determined by conventional Edman degradation of the reduced and vinylpyridinated enz ymes and peptides hereof generated by cleavage with cyanogen bromide, iodobenzoic acid, glutamic acid cleaving enzyme, AspN-endoproteinase a nd EndoLysC proteinase. CPD-I consists of a single peptide chain of 47 1 amino acid residues, three disulfide bridges and nine N-glycosylated asparaginyl residues, while CPD-II consists of a single peptide chain of 481 amino acid residues, has three disulfide bridges, one free cys teinyl residue and nine glycosylated asparaginyl residues. The enzymes are closely related to carboxypeptidase S3 from Penicillium janthinel lum. Both Ca2+ and Mg2+ stabilize CPD-I as well as CPD-II, at basic pH values, Ca2+ being most effective, while the divalent ions have no ef fect on the activity of the two enzymes. (C) 1998 Elsevier Science B.V . All rights reserved.