gamma-Aminobutyric acid transaminase (GABAT) polymorphism among ethnic groups in Singapore--with report of a new allele.

gamma-Aminobutyric acid transaminase (GABAT, E.C.2.6.I.19) was phenotyped by starch-gel electrophoresis in post-mortem liver samples from 650 unrelated subjects of either sex, comprising 289 Chinese, 177 Indians, 140 Malays, and 44 from other racial groups from Southeast Asia. The estimated gene frequencies of GABAT1 and GABAT2 were found to be .5779 and .3806 in Chinese, .5678 and .3955 in Indians, and .6214 and .3250 in Malays. The frequency of GABAT1 was .5909 in the mixed group of other races. There was no significant difference in the phenotypic distribution between sexes. A new slow (less anodal) variant (GABAT3) has been observed in low frequency in all the groups (.0415, .0367, 0536, and 0536, and .0568 in Chinese, Indians, Malays, and the mixed-group, respectively). The distribution of GABAT phenotypes was at Hardy-Weinberg equilibrium in all the ethnic groups studied.