MOLECULAR-CLONING AND SEQUENCE-ANALYSIS OF THE SCPZ GENE ENCODING THE SERINE CARBOXYPEPTIDASE OF ABSIDIA-ZYCHAE

Carboxypeptidase Z is a serine carboxypeptidase secreted by Absidia zychae NRI0 1199. The cDNA and genomic DNA carrying the scpZ gene encoding carboxypeptidase Z were cloned and sequenced. The nucleotide sequences of the cDNA (1.4 kb) and the genomic DNA (3.3 kb) were analyzed and the intervening sequences were located by a comparison of the two. It was found that the scpZ gene was interrupted by 11 short introns, 50-75 nucleotides in length. Genomic Southern analysis showed that there was only one scpZ gene in the genome of A. zychae. The gene encoded a putative pre-proenzyme composed of 409 amino-acid residues of the mature carboxypeptidase Z (Mr 45 421) and an additional N-terminal sequence of 51 amino-acid residues. The amino-acid sequence around the active serine residue of carboxypeptidase Z (-G-E-S-Y-G-G-) differed from the consensus (-G-E-S-Y-A-G-) which is conserved in most of the serine carboxypeptidases so far analyzed.