CHARACTERIZATION OF A VARIANT GLUCOSE-6-PHOSPHATE-DEHYDROGENASE FROM THE SOUTH INDIAN POPULATION

Glucose-6-phosphate dehydrogenase (G6PD) is coded by a gene on the X-c hromosome. Earlier studies have shown that the South Indian population has a high incidence of this enzyme deficiency. The electrophoretic m obility, pH optimum and the K-m values for G6PD from normal and varian t individuals were identical. However, the specific activity of the va riant enzyme was 8 times less compared to the value of the normal enzy me. Western blot analysis of partially purified G6PD from normal and v ariant individuals performed using equal amounts of total protein show ed that the variant protein was 3 times less in concentration. Similar analysis performed using protein corresponding to equal enzyme activi ty units in the normal and variant samples showed that the variant enz yme was 2.25 times less efficient compared to the normal enzyme. RNA d ot blot analysis using full length G6PD cDNA probe (PGDT5B, a kind gif t from Prof. L Luzzatto) revealed that lymphocytes from normal and var iant individuals had equal amounts of G6PD specific mRNA.