Ono S, Tsutsui M, Gonzalez F J, Satoh T, Masubuchi Y, Horie T, Suzuki T, Narimatsu S
Central Laboratory, Amersham K. K., Chiba, Japan.
Pharmacogenetics. 1995 Apr;5(2):97-102. doi: 10.1097/00008571-199504000-00006.
We examined the oxidative metabolism of a beta-blocker bunitrolol (BTL) by 10 human cytochromes P450 (CYP) (1A2, 2A6, 2B6, 2C8, 2C9, 2D6, 2E1, 3A3, 3A4 or 3A5), which were individually expressed in Hep G2 cells with a vaccinia virus complementary DNA expression system. Among the 10 isozymes, only CYP2D6 and 1A2 at a substrate concentration of 5 microns, and CYP2C8 and 2C9 in addition to the two isozymes at a BTL concentration of 1 mM, exhibited detectable BTL 4-hydroxylase activities. The activities at 1 mM BTL were on the order of CYP2D6 (100% as relative activity) > CYP1A2 (86%) >> CYP2C8 and 2C9 (7-8%). Enzyme kinetic parameters of CYP2D6 were calculated to be 4.41 microns as a Km value and 0.442 nmol min-1 per nmol CYP as a Vmax value. Kinetic parameters of CYP1A2 were calculated as 295 microns and 0.411 nmol min-1 per nmol CYP for Km and Vm values, respectively. These results suggest that both CYP2D6 and 1A2 primarily catalyse BTL 4-hydroxylation, but that the former is a predominant isozyme responsible for the reaction at a low substrate concentration range of BTL in human liver.
我们通过10种人细胞色素P450（CYP）（1A2、2A6、2B6、2C8、2C9、2D6、2E1、3A3、3A4或3A5）研究了β受体阻滞剂布尼洛尔（BTL）的氧化代谢，这些细胞色素P450在Hep G2细胞中通过痘苗病毒互补DNA表达系统单独表达。在这10种同工酶中，仅在底物浓度为5微米时CYP2D6和1A2，以及在BTL浓度为1 mM时除这两种同工酶外的CYP2C8和2C9表现出可检测到的BTL 4-羟化酶活性。在1 mM BTL时的活性顺序为CYP2D6（相对活性为100%）> CYP1A2（86%）>> CYP2C8和2C9（7 - 8%）。计算得出CYP2D6的酶动力学参数，Km值为4.41微米，Vmax值为每纳摩尔CYP 0.442纳摩尔/分钟。CYP1A2的动力学参数计算得出，Km值为295微米，Vm值为每纳摩尔CYP 0.411纳摩尔/分钟。这些结果表明，CYP2D6和1A2均主要催化BTL的4-羟化反应，但在人肝脏中低底物浓度范围的BTL条件下，前者是负责该反应的主要同工酶。
