Variation in the primary structure of carbonic anhydrase B in man, great apes, and old world monkeys.

-The amino acid compositions and sequences of 15 homologous tryptic peptides of carbonic anhydrase B from man and 7 Old World primates were compared. Of the 133 residues examined, differences were noted at 8 presumably homologous sites. Chimpanzee and man differed at only one site, whereas orangutan and man differed at four sites. The four monkey species differed from man by four to 6 residues. The fixation rates for mutations of these carbonic anhydrases appear to be similar to those found for the hemoglobin chains of the same species. Two genetically distinct isozymes of erythrocyte carbonic anhydrase, designated CA B and CA C, or CA I and CA II, have now been purified from the hemolysates of man (cf. 1,2) and a number of other primate species (3,4). Because the primary amino acid sequence of the human CA B isozyme has been determined for about 205 of its approximately 265 residues (2,5), it is now possible to begin to compare the sequences of the homologous CA B enzymes from different primates. In the present communication, we have compared the amino acid sequences or compositions in 15 homologous tryptic peptides of CA B purified from man, the great apes--chimpanzee (Pan troglodytes) and orangutan (Pongo Pygmaeus), and the Old World monkeys-green monkey (Cercopithecus aethiops), common baboon (Papio cynocephalus), rhesus macaque (Macaca mulatta), -and cynomolgous macaque (Macaca irus). -These peptides were composed of 133, or about 5C$, of the approximately 265 residues which make up the single polypeptide chain of human CA B.