title: Liver microsomal drug-metabolizing enzyme system: functional components and their properties.
abstract: The liver microsomal drug-metabolizing enzyme system consists of two protein components, cytochrome P-450 and NADPH-cytochrome c reductase, and a lipid, phosphatidylcholine. Cytochrome P-450 serves as the binding site for oxygen and substrate while the reductase acts as an electron carrier shuttling electrons from NADPH to cytochrome P-450. The phospholipid facilitates the transfer of electrons from NADPH-cytochrome c reductase to cytochrome P-450 but itself is not an electron carrier. Different cytochromes P-450 and P-448 have been purified; the spectral, catalytic, and immunological properties as well as the molecular weight (determined by SDS-gel electrophoresis) of all these hemeproteins differ from one another. The presence of multiple cytochrome P-450s may explain the species, strain, age, tissue, and sex differences as well as the effect of inducers and nutritional status in mammlian drug metabolism.
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003579:Cytochrome Reductases / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism; D050356:Lipid Metabolism; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D009747:Nutritional Physiological Phenomena; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D011506:Proteins / Q000502:physiology; D011817:Rabbits; D051381:Rats; D012643:Selenium / Q000494:pharmacology; D013045:Species Specificity
chemical_list: D003580:Cytochromes; D004364:Pharmaceutical Preparations; D011506:Proteins; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D003579:Cytochrome Reductases; D009251:NADPH-Ferrihemoprotein Reductase; D012643:Selenium