Kinetic studies on glucose-06-phosphate dehydrogenase. I. Inhibition by dipiridamole

Abstract

It has been investigated the modifications of the activity of the G6PD by DPD; the study of the enzimatic kinetics in function of the sustrate concentrations (G6P) has shown that it’s a competitive inhibitor.

In the experimental conditions we worked, the value of Ki obtained for DPD is 7 X 10-4 M and the grade of inhibition caused by DPD is 15 % for 0.1 mM and 20 % for 0.5 mM.

When we study the kinetics of the reaction in function of various NADP concen­ trations, DPD behavies as a non-competitive inhibitor of the G6PD. The obtained values of Vmax are 0.163AA3lo min-1 in absence of DPD, 0.147AA,lo min-1 in presence of DPD 0.05 mM and 0.135AAllo min-1 in presence of DPD 0.1 mM.

When the enzimatics kinetics is studied in function of NADP, the value of Ki for DPD is 5.8 X 10-4 M, the grade of inhibition is 10 and 16 % for DPD 0.05 and 0.1 mM respectively.

From these experiencies it’s concluded that one of the metabolic actions of DPD may be to induce a deviation of glucose degradation into the glucolitic pathway, in­ creasing ATP synthesis.

Present findings are related to that obtained with this drug wich acts also as a com­ petitive inhibitor of adenosin-desaminase.