Glucose-6-phosphate oxidation pathway in rat-liver microsomal vesicles. Stimulation under oxidative stress

The glucose-6-phosphate oxidation pathway present in microsomes was studied using intact microsomal membranes. The oxidation activity, which was measured by monitoring the formation of 14CO2 from [1-14C]glucose 6-phosphate, was greatly stimulated when azodicarboxylic acid bis(dimethylamide), methylene blue or cumene hydroperoxide was added to the assay mixture. Glutathione peroxidase and glutathione reductase are suggested to be involved in the oxidation reaction induced by these oxidizing reagents. We detected a significant activity of the glutathione reductase inherent to microsomes. The microsomal glutathione reductase is latent and requires detergent to reveal its activity. 4,4'-Diisothiocyanostilbene 2,2'-disulfonic acid (DIDS) inhibited the 14CO2 formation, but the inhibition was released by the addition of a detergent. Moreover, the inhibitory effect of DIDS was reversed by glucose 6-phosphate but not by mannose 6-phosphate. We conclude that the glucose-6-phosphate oxidation pathway in intact microsomes starts working under oxidative stress and that a transporter specific for glucose 6-phosphate is involved in the reaction.