Abstract
Starch gel electrophoretic patterns of carbonic anhydrase (CA) isozymes were examined from tissue extracts of sheep, mice, rabbits, and chickens. In addition to the widely distributed and extensively studied B and C isozymes, an additional isozyme (called CA‐A) was observed, which was predominantly localized in muscle tissue. Immunochemical studies showed the A isozyme to be homologous with CA‐B. Developmental and tissue distribution analyses suggested that a third locus (A) is involved in carbonic anhydrase synthesis in mammals.