Human hepatic metabolism of the anti-osteoporosis drug eldecalcitol involves sterol C4-methyl oxidase.
Human hepatic metabolism of the anti-osteoporosis drug eldecalcitol involves sterol C4-methyl oxidase.
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DOI：
10.1002/prp2.120
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发表时间：
2015-03
影响因子：
2.6
通讯作者：
Sakaki, Toshiyuki
中科院分区：
文献类型：
--
作者：
Yasuda, Kaori;Iwanaga, Yuasa;Ogawa, Kazuaki;Mano, Hiroki;Ueno, Sera;Kimoto, Shutaro;Ohta, Miho;Kamakura, Masaki;Ikushiro, Shinichi;Sakaki, Toshiyuki
用体外系统研究了维生素D3活性形式的2-羟基丙氧基化类似物--依地骨化醇(ED-71)的代谢。ED-71在人的小肠和肝脏微粒体中代谢为1α，2β，25-三羟基维生素D3(1α，2β，25(OH)3D3)。为了确定参与这种代谢的酶，我们通过重组的属于CYP1、2和3个家族的P450亚型来检测NADPH依赖的代谢，发现CYP3A4具有这种活性。然而，CYP3A4特异性抑制剂酮康唑只使人肝微粒体中的活性降低了36%，这表明其他酶可能参与了ED-71的代谢。由于氰化物显著抑制新陈代谢，我们推测类固醇C4-甲基氧化酶基因产物(SC4MOL)可能与ED-71的代谢有关。值得注意的是，SC4MOL是胆固醇合成的生理必需物质。在COS7、酿酒酵母或大肠杆菌中表达的重组人SC4MOL可将ED-71转化为1α，2β，25(OH)3D3。此外，我们还利用重组细胞色素P24A1对ED-71的代谢进行了评价，它在维生素D3活性形式(1α，25(OH)2D3)及其类似物的代谢中起着重要作用。ED-71的24或23-羟基化的kcat/Km值仅为1α，25(OH)2D3的3%，表明ED-71对细胞色素P24A1依赖的分解代谢有抵抗作用。在催化ED-71的三种酶中，SC4MOL在ED-71的代谢中起着最重要的作用。据我们所知，这是第一个表明SC4MOL可以作为药物代谢酶发挥作用的研究。SC4MOL的酵母和大肠杆菌表达系统可用于SC4MOL的结构和功能分析。
The metabolism of eldecalcitol (ED-71), a 2β-hydroxypropoxylated analog of the active form of vitamin D3 was investigated by using in vitro systems. ED-71 was metabolized to 1α,2β,25-trihydroxyvitamin D3 (1α,2β,25(OH)3D3) in human small intestine and liver microsomes. To identify the enzymes involved in this metabolism, we examined NADPH-dependent metabolism by recombinant P450 isoforms belonging to the CYP1, 2, and 3 families, and revealed that CYP3A4 had the activity. However, the CYP3A4 -specific inhibitor, ketoconazole, decreased the activity in human liver microsomes by only 36%, suggesting that other enzymes could be involved in ED-71 metabolism. Because metabolism was dramatically inhibited by cyanide, we assumed that sterol C4-methyl oxidase like gene product (SC4MOL) might contribute to the metabolism of ED-71. It is noted that SC4MOL is physiologically essential for cholesterol synthesis. Recombinant human SC4MOL expressed in COS7, Saccharomyces cerevisiae, or Escherichia coli cells converted ED-71 to 1α,2β,25(OH)3D3. Furthermore, we evaluated the metabolism of ED-71 by recombinant CYP24A1, which plays an important role in the metabolism of the active form of vitamin D3 (1α,25(OH)2D3) and its analogs. The kcat/Km value for 24- or 23-hydroxylation of ED-71 was only 3% of that for 1α,25(OH)2D3, indicating that ED-71 was resistant to CYP24A1-dependent catabolism. Among the three enzymes catalyzing ED-71, SC4MOL appears to be most important in the metabolism of ED-71. To the best of our knowledge, this is the first study showing that SC4MOL can function as a drug-metabolizing enzyme. The yeast and E. coli expression systems for SC4MOL could be useful for structure-function analyses of SC4MOL.