Characterization of an inhibitor of glucose-06-phosphate dehydrogenase

Abstract

A strong inhibitor of G6PDH has been detected in rat liver homogenates.The inhibitor, isolated by ultrafiltration methods, proved to be very stable under incubation with trypsin and high temperatures.Gel-filtration through Sephadex G-75 showed it to have a molecular weight of 3,500 daltons, though perchloric acid treatment produced a light form of 900 daltons.Both forms of inhibitor act as competitive inhibitor with respect to G6P and exhibit non-competitive inhibition pattern with respect to NADP+.Physical and kinetic properties, and the increase of G6PDH activity at low NADP+ concentrations, in the presence of NADPH and inhibitor or palmitoyl-CoA, in relation to the G6PDH activity in presence of NADPH, lead to the identification of the low-molecular weight inhibitor as palmitoyl-CoA.