title: Debrisoquine-type polymorphism of drug oxidation: purification from human liver of a cytochrome P450 isozyme with high activity for bufuralol hydroxylation.
abstract: Indirect evidence suggests that the genetically defective metabolism of drugs such as debrisoquine and bufuralol observed in up to 10% of the population (poor metabolizers) is caused by the absence or functional deficiency of a cytochrome P450 isozyme. Using bufuralol-1'-hydroxylation to carbinol to optimize the procedure, 3 cytochrome P450 isozymes (P450A, P450buf, P450C) were purified to apparent electrophoretic homogeneity from human liver microsomes. P450buf had a specific activity of 20.3 nmol carbinol X nmol P450-1 X 15 min-1 as compared to microsomes (10.0 nmol carbinol X nmol P450(-1) X 15 min-1) when (+)-bufuralol was used as substrate. The stereoselective metabolism of (-)- and (+)-bufuralol to carbinol by purified P450buf [(-)/(+) ratio: 0.13] was strikingly different from that in the microsomes of either an extensive [(-)/(+) ratio: 0.4] or poor metabolizer [(-)/(+) ratio: 0.83] of bufuralol. We propose that this isozyme is the major bufuralol and debrisoquine hydroxylating species and is the target of the genetic deficiency.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D003647:Debrisoquin / Q000378:metabolism*; D004983:Ethanolamines / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D007527:Isoenzymes / Q000235:genetics* / Q000302:isolation & purification; D007546:Isoquinolines / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism*; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011110:Polymorphism, Genetic; D013379:Substrate Specificity
chemical_list: D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D007527:Isoenzymes; D007546:Isoquinolines; C010831:bufuralol; D003577:Cytochrome P-450 Enzyme System; D003647:Debrisoquin