Activity of key enzymes in microsomal and mitochondrial membranes depends on the redox reactions involving lipid radicals.
The work reviews membrane processes, such as monooxygenase reaction and oxidative phosphorylation with special reference to hydroxylation of a xenobiotic benzo(a)pyrene and the effects of the radical scavenger propyl gallate and radical generator Fe2+ ions on the reaction kinetics. A possibility is discussed that tocopherol provides for the activity of the lipid-radical cycles involving cytochrome b5. The lipid-radical cycles protect membrane lipids from oxidation and control the kinetics of membrane processes. The NADPH oxidation energy is transformed into the energy of lipid pulsations and this energy is used for activation of membrane enzymes. To account for the role of lipid pulsations in membrane processes, a new parameter is introduced - the internal temperature. It is supposed that there should be the equilibrium between the pro- and antioxidant factors in the membranes, and the presence of exogenous antioxidants (propyl gallate etc.) should be considered as a negative factor.
Dmitriev
L F
LF
School of Biology, Lomonosov Moscow State University, Russia. Dmitriev@mars.bophys.msu.ru
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001564:Benzo(a)pyrene / Q000378:metabolism; D002412:Cations / Q000737:chemistry / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015786:Cytochromes b5 / Q000378:metabolism*; D004579:Electron Transport; D004789:Enzyme Activation; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals; D006900:Hydroxylation; D007425:Intracellular Membranes / Q000201:enzymology*; D007501:Iron / Q000737:chemistry / Q000494:pharmacology; D015227:Lipid Peroxidation; D008563:Membrane Lipids / Q000378:metabolism*; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D008954:Models, Biological; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D010766:Phosphorylation; D011435:Propyl Gallate / Q000494:pharmacology; D011487:Protein Conformation; D013696:Temperature; D024505:Tocopherols / Q000494:pharmacology; D014451:Ubiquinone / Q000378:metabolism
D000975:Antioxidants; D002412:Cations; D005231:Fatty Acids, Unsaturated; D016166:Free Radical Scavengers; D005609:Free Radicals; D008563:Membrane Lipids; D008565:Membrane Proteins; D009243:NAD; D014451:Ubiquinone; D001564:Benzo(a)pyrene; D009249:NADP; D000244:Adenosine Diphosphate; D011435:Propyl Gallate; D000255:Adenosine Triphosphate; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D007501:Iron; D019255:NADPH Oxidases; D024505:Tocopherols