Human platelet glucose-6-phosphate dehydrogenase. Total purification, kinetic studies and relationship with enzyme from other blood cells

Abstract

Human platelet G-6-PD has been highly purified, to homogeneity, and its kinetic, electrophoretic and immunological characteristics have been studied. Platelet G-6-PD differs from erythrocyte or leukocyte enzymes by an increased Michaelis constant for G-6-P and a slow activity at the acid pHs. By electrofocusing only a main active band (band a) of platelet G-6-PD was found. The incubation at 37 degrees C in the presence of NADP+ and dithiothreitol normalize Km-G-6-P of platelet G-6-PD; the incubation with boiled and ultrafiltered leukemic granulocyte extracts led to an anodisation of G-6-PD active forms, a decrease of the molecular specific activity and a further increase of Km-G-6-P; these last modifications are the same as those undergone by G-6-PD incubated in crude extracts of normal or leukemic granulocytes.