title: [Regulation mechanisms of the endoplasmic cytochrome P-450 systems of the liver].
abstract: Regulation mechanisms of the cytochrome P-450 dependent monooxygenase from the hepatic endoplasmic reticulum at 3 different integrational levels are discussed. At the molecular level the activity of the system is regulated by a substrate dependent shift of an equilibrium of cytochrome P-450 spin conformers in favour of the high spin component. A correlation between the extent of the spin shift, the reduction rate and the substrate turnover has been evidenced. The regulation at the membrane level is based on interactions between the 3 essential components of the system: cytochrome P-450, reductase and lipid. The formation of the cytochrome P-450-reductase-complex necessary for oxygen activation by transfer of electrons is dependent on the charge of the phospholipids. The binding constant of the donor-acceptor complex increases with the acidity of the phospholipid head group, thus enhancing the velocity of the electron transfer.
mesh_terms: D000818:Animals; D001711:Biotransformation; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004579:Electron Transport; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005260:Female; D006728:Hormones / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008214:Lymphocytes / Q000201:enzymology; D008297:Male; D010105:Oxygenases / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
chemical_list: D006728:Hormones; D007527:Isoenzymes; D010743:Phospholipids; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases
vernacular_title: Regulationsmechanismen des endoplasmatischen Zytochrom P-450-Systems der Leber.