Studies on human erythrocyte glutathione-S-transferase from HbAA, HbAS and HbSS subjects.

Abstract

The activities of human erythrocyte glutathione-S-transferase (EC 2.5.1.18) obtained from 53 subjects of both sexes aged between 5 and 25 years of HbAA (20), HbAS (13) and HbSS (20) were determined. The results, expressed in IU/g Hb, obtained for the various genotypes were: HbSS = 14.6 +/- 3.4; HbAS = 4.7 +/- 1.1; HbAA = 2.7 +/- 0.8. The observed differences were found to be statistically significant (p less than 0.001). Kinetic analysis showed similar Michaelis constants (Km) of the enzyme irrespective of the genotype, indicating structural and functional similarities of the enzyme from the various genotypes. A mean (+/- SD) percentage increase of 63.8 +/- 4.9 was obtained for the red cell glutathione-S-transferase activity in the presence of dithionite, while a mean (+/- SD) decrease of 38.8 +/- 1.9% was obtained in the presence of 0.3 mM haemin. These findings suggest an increased activation of the enzyme in HbSS and HbAS subjects (as compared with HbAA subjects) possibly by an increased generation of electrophilic substrates in the red cell of these subjects.