Cankaya, M.; Sisecioglu, M.; Ciftci, M.; Ozdemir, H.

Information on the mechanism of metal ion inhibition of Glucose 6-phosphate dehydrogenase (G6PD) is limited. The purpose of the present study was to clarify in vitro effect of Hg +2, Cd +2, Pb +2, Fe +2, Cu +2 and Zn +2ions on the purified glucose 6-phosphate dehydrogenase (G6PD). This enzyme was purified from rainbow trout liver (Oncorhynchus mykiss) by 2',5'-ADP sepharose 4B affinity gel chromatography. G6PD was purified 1010-fold with a yield of 41.72%. Purity of enzyme checked by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) method and a single band was observed. All of the metal ions caused inhibition of the enzyme activity. Of the metal ions tested, Fe +2 exhibited much higher inhibitory effect at lower concentrations, so it was evidently a more potent inhibitor than the others. Hg +2, Cd +2, Pb +2, Cu +2 and Zn +2 displayed noncompetitive type of inhibition mechanism only Fe +2 exhibited competitive type inhibition. IC 50 value of Fe +2, Pb +2, Hg +2, Cu +2, Zn +2 and Cd +2 were 0.39, 0.78, 0.87, 1.19, 1.97, 2.16 and the Ki constants 0.197±0.049, 0.213±0.018, 0.542±0.029, 1.721±0.77, 2.034±0.53 and 2.770±1.21, respectively.