A GPT silent allele found in a case with acute exacerbation of HBV carrier

Soluble fraction of GPT (sGPT) exhibits genetic polymorphism by two autosomal codominant alleles, Gpt1 and Gpt2 The catalytic activity of the Gpt1 product is 2-3 times higher than that of Gpt2. The existence of a silent allele (Gpt0) has also so far been predicted by several authors. The proband, a 47-year-old female with acute exacerbation of HBV carrier, showed a remarkably low value of serum GPT activity, comparing with the elevated value of GOT, LDH, ALP at admission. In red cell lysates the GPT activity was 0.82U/gHb and a very weak band in its electrophoresis corresponded with the phenotype GPT2, GPT phenotype and activity of her mother were GPT1 and 2.93U/gHb, respectively. Low value of GPT in red cell lysates and a discrepancy in phenotype between the mother and the proband could be explained by the existence of Gpt0 which does not participate in determining the phenotypes.