Characterization of human liver microsomal cytochrome P450 involved in the reductive metabolism of zonisamide.
Characterization of human liver microsomal cytochrome P450 involved in the reductive metabolism of zonisamide.
复制标题
人肝微粒体细胞色素 P450 参与唑尼沙胺还原代谢的表征。
作者：
H. Nakasa;M. Komiya;S. Ohmori;T. Rikihisa;M. Kiuchi;M. Kitada
在厌氧条件下，唑尼沙胺（1，2-苯并异恶唑-3-甲磺酰胺）在人肝微粒体中代谢为2-氨磺酰乙酰苯酚（SMAP）。西咪替丁，正辛胺，酮康唑，和一氧化碳显着抑制SMAP的形成，表明细胞色素P450参与代谢唑尼沙胺SMAP在人肝微粒体。SMAP产生活性与细胞色素P450的光谱测定量不相关。相反，唑尼沙胺的SMAP产生活性与睾酮6 β-羟化酶的活性密切相关（r2 = 0.96），与丙咪嗪2-羟化酶的活性轻微但显著相关（r2 = 0.28），但与苯胺羟化酶（r2 = 0.09）或苄非他明N-脱甲基酶（r2 = 0.20）的活性无关。此外，21例人肝微粒体中细胞色素P450酶的免疫定量显示，SMAP形成与人肝微粒体中P450 3A酶的量密切相关，与P450 2D 6的量中度相关，但与P450 2C酶的量无关。P450 3A 4在重组单加氧酶系统中表现出产生SMAP的活性。抗P450 3A 4抗体几乎完全抑制唑尼沙胺代谢为SMAP，而抗P450 2C 9或抗P450 2D 6抗体则不抑制唑尼沙胺代谢为SMAP，提示P450 3A酶的量可能是影响唑尼沙胺在人肝微粒体中代谢为SMAP水平的主要因素。
Zonisamide (1,2-benzisoxazole-3-methanesulfonamide) was metabolized to 2-sulfamoylacetylphenol (SMAP) in human liver microsomes under anaerobic conditions. The formation of SMAP was remarkably inhibited by cimetidine, n-octylamine, ketoconazole, and carbon monoxide, indicating that a cytochrome P450 is involved in the metabolism of zonisamide to SMAP in human liver microsomes. The SMAP-producing activity did not correlate with the spectrally determined amount of cytochrome P450. In contrast, the SMAP-producing activity from zonisamide correlated closely with the activity of testosterone 6 beta-hydroxylase (r2 = 0.96) and correlated slightly but significantly with the activity of imipramine 2-hydroxylase (r2 = 0.28), but not with those of aniline hydroxylase (r2 = 0.09) or benzphetamine N-demethylase (r2 = 0.20). In addition, immunoquantitation of cytochrome P450 enzymes in 21 human liver microsomal samples revealed that SMAP formation correlated closely with the amount of P450 3A enzyme and correlated moderately well with that of P450 2D6 but not with that of P450 2C enzyme in human liver microsomes. P450 3A4 exhibited SMAP-producing activity in a reconstituted monooxygenase system. The metabolism of zonisamide to SMAP was almost completely inhibited by anti-P450 3A4 antibody but not by anti-P450 2C9 or anti-P450 2D6 antibodies, suggesting that the amount of P450 3A enzyme may be a major factor influencing the level of metabolism of zonisamide to SMAP in human liver microsomes.