Human carboxypeptidase A identifies a BglII RFLP and maps to 7q31-qter

A genomic clone for human carboxypeptidase has been isolated with a probe for rat CPA1 cDNA. A 1.7-kb HindIII/EcoRI fragment from the 3' flanking region of human carboxypeptidase detects a DNA polymorphism with BglIII. Multipoint linkage analysis with an established map of chromosome 7 markers shows that the most likely location of carboxypeptidase is at 7q31-qter, between D7S87 and D7S93. All other placements can be excluded with odds greater than 100:1. These and other markers confirm that carboxypeptidase lies distal to the locus for cystic fibrosis, at a distance of approximately 12 centimorgans. The regions containing identity to the rat gene were sequenced and shown to be 82% identical to exons 9 and 10 of the rat gene. The presence of a codon for isoleucine at the residues corresponding to codon 255 of rat CPA1 cDNA strongly suggests that the A form of human carboxypeptidase has been isolated.