Chemical characterization of a new Japanese variant of carbonic anhydrase I, CA INagasaki 1 (76 arg leads to gln).

A new inherited variant of carbonic anhydrase I (CA I), designated CA INagasaki 1 (CA INGS 1), was discovered during a survey of hemolysates from 5852 individuals from the cities of Hiroshima and Nagasaki in Japan. Analysis of the amino acid composition of a tryptic peptide from the CA INGS 1 variant indicated that a glutaminyl residue was substituted for an arginyl residue at position 76. Heat degradation studies showed that the CA INGS 1 variant was less stable than normal CA I. The CO2 hydrase and esterase activities of the normal and variant carbonic anhydrases I, as well as the relative amounts of the two enzymes in heterozygotes, were similar.