Explanation of the stimulation of microsomal N-demethylation reactions by soluble supernatant fraction.
Addition of the cell soluble supernatant fraction to an assay medium containing NADPH generating system, mixed function oxidase substrate and microsomes, resulted in a stimulation of drug metabolism ranging from 12-75%. This stimulation was observed only when the supply of DADPH generating system (isocitric dehydrogenase or glucose 6 phosphate dehydrogenase) was insufficient, leading to a NADPH oxidation rate which was greater than the rate of reduction of NADP+ during the oxidation of a drug. Hence, under our assay conditions, the soluble supernate (SS) is only providing sufficient NADPH generator, and possibly relieving inhibition by the generated NADP+. Finally, microsomal lipid peroxidation measurements under these same conditions indicate negligible to no peroxidation activity in the absence of SS.
D000633:Aminopyrine N-Demethylase / Q000378:metabolism; D000818:Animals; D003640:Dealkylation; D005037:Ethylmorphine-N-Demethylase / Q000378:metabolism; D005260:Female; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D051381:Rats; D013268:Stimulation, Chemical; D013347:Subcellular Fractions / Q000502:physiology*; D013997:Time Factors
D009249:NADP; D000633:Aminopyrine N-Demethylase; D005037:Ethylmorphine-N-Demethylase