title: Polyamines as modulators of drug oxidation reactions catalyzed by cytochrome P-450 from liver microsomes.
abstract: The effect of polyamines on the activity of the mixed-function oxidase (MFO) system from human, rat and rabbit liver microsomes was investigated in detail. It was shown that polyamine (spermine) stimulates NADPH-dependent activity of the MFO system several-fold whatever the substrate (foreign drug or natural), not only with microsomes but also with the reconstituted system consisting of highly purified cytochrome P-450 (LM2 isozyme), cytochrome P-450 NADPH reductase and dilauroylphosphorylcholine. Stimulation (extent and concentration dependence) appeared to be dependent on a number of parameters such as ionic strength, pH, animal species and treatment, nature of the substrate, and was stereospecific (different effect on 6 beta-and 16 alpha-testosterone hydroxylation). Further, the spermine effect was evaluated on some elementary steps of the cytochrome P-450 reaction cycle, like substrate binding, P-450 reduction and second electron transfer. Finally, it was shown that the organic peroxide dependent activity was not stimulated by spermine with microsomes nor with the purified P-450 LM2 isozyme. On the basis of this study, it was concluded that the locus of polyamine action is cytochrome P-450 and that stimulation could result either from increased stability of the oxyferrous intermediate of P-450 or from an increased rate of second electron transfer from reductase to P-450.
mesh_terms: D000818:Animals; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013096:Spermine / Q000494:pharmacology
chemical_list: D011073:Polyamines; D013096:Spermine; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases