Genetic variants of red cell enzymes as potential anthropological markers in the Western Pacific

During the population genetic surveys of the aboriginal Negrito groups of the Philippines, "rare" variants of carbonic anhydrase-1 (CA1), adenylate kinase (AK) and esterase D (ESD) were discovered with remarkably high frequencies. The variant CAS1 isozyme discovered among the Mamanwa tribe of northeastern Mindanao was electrophoretically indistinguishable from the "Guam" variant. Subsequent study of peptide mapping and amino acid analysis showed that they are in fact identical. The frequency of the variant allele was estimated at 0.20-0.25. The AK variant had an estimated frequency of 0.07 among the Aeta of Luzon. The fact that these variants occur sporadically in wide areas in the western Pacific suggests that they have been spread by gene diffusion from the aboriginal populations of this area, from which the present Negrito probably are derived.