title: Regio- and stereoselectivity in propranolol metabolism by dog liver microsomes and the expressed dog CYP2D15.
abstract: We have studied the regio- and stereoselectivity of ring-hydroxylation and N-desisopropylation of S(-)- and R(+)-propranolol, using dog liver microsomes and the expressed dog CYP2D15 in insect cells. In dog liver microsomes, 4-hydroxylation was the preferred pathway in S(-)-propranolol oxidation, while N-desisopropylation was the preferred pathway in R(+)-propranolol oxidation. S(-)-Propranolol was preferred over R(+)-propranolol as substrate for 4- and 5-hydroxylations, while R(+)-propranolol was the preferred substrate for N-desisopropylation at higher substrate concentrations. The expressed CYP2D15 had high catalytic activities toward 4-, 5-hydroxylation, as well as N-desisopropylation of both enantiomers. At the substrate concentrations used, 4-hydroxylation was the preferred pathway for the metabolism of both enantiomers, and S(-)-propranolol was the preferred substrate over R(+)-propranolol for all three monooxygenations catalyzed by CYP2D15. Anti-CYP2D15 peptide antibody strongly inhibited 4- and 5-hydroxylation of both enantiomers in dog liver microsomes, while it did not inhibit their N-desisopropylation. These findings suggest that CYP2D15 is highly responsible for the stereoselective 4- and 5-hydroxylations of propranolol in dog liver microsomes.
authors.affiliation: Laboratory of Toxicology, Department of Environmental Veterinary Medical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, N18, W9, Kita-ku, Sapporo 060.
authors.forename: T
authors.initials: T
authors.lastname: Tasaki
authors.forename: H
authors.initials: H
authors.lastname: Iwata
authors.forename: A
authors.initials: A
authors.lastname: Kazusaka
authors.forename: S
authors.initials: S
authors.lastname: Fujita
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002384:Catalysis; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004285:Dogs; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D011433:Propranolol / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D018411:Spodoptera; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D011433:Propranolol; D001189:Aryl Hydrocarbon Hydroxylases; C110942:cytochrome P-450 CYP2D15 (dog); D010100:Oxygen