The inhibitory effects of some pesticides on human erythrocyte glucose-6-phosphate dehydrogenase activity (in vitro)

Abstract

Human erythrocyte glucose-6-phosphate dehydrogenase was purified to apparent homogeneity by salting out with ammonium sulfate and applying one chromatographic step with the commercially available resin 2',5'-ADP Sepharose 4B. The enzyme, having a specific activity of 70.7 U/mg protein, was purified 7069 fold with an overall enzyme yield of 33.6%. The purity and molecular mass of the protein was confirmed with SDS-PAGE. The purified glucose-6-phosphate dehydrogenase was effectively active on glucose-6-phosphate and NADP(+). with Km values of 0.22 and 0.14 mM and Vmax values of 1.94 and 2.76 U/mg, respectively. The in vitro effects of commonly used pesticides Glyphosate (TM) (N-(Phosphonomethyl) glycine) and 2,4D (TM) (2,4-Dichlorophenoxyacetic acid) were determined on the purified glucose-6-phosphate dehydrogenase. Both pesticides were effective inhibitors on the activity with IC50 values of 32.35 and 38.34 mM, respectively. The interaction kinetics of Glyphosate (TM) and 2,4D (TM) with the purified enzyme indicated uncompetitive and competitive inhibition patterns with Ki values of 13.45 and 8.45 mM, respectively.