Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA; Department of Pharmacology and Toxicology, College of Pharmacy, University of Karbala, Karbala, Iraq.
Department of Pharmacology, College of Pharmacy and Pharmaceutical Sciences, University of Toledo Health Science Campus, Toledo, USA; Department of Pharmacology and Toxicology, College of Pharmacy, University of Kufa, Kufa, Iraq.
Pharmacol Rep. 2017 Oct;69(5):953-958. doi: 10.1016/j.pharep.2017.02.014. Epub 2017 Feb 16.
Previous studies have demonstrated that sulfate conjugation is involved in the metabolism of the active metabolite of tramadol, O-desmethyltramadol (O-DMT). The current study aimed to systematically identify the human cytosolic sulfotransferases (SULTs) that are capable of mediating the sulfation of O-DMT.
The sulfation of O-DMT under metabolic conditions was demonstrated using HepG2 hepatoma cells and Caco-2 human colon carcinoma cells. O-DMT-sulfating activity of thirteen known human SULTs and four human organ specimens was examined using an established sulfotransferase assay. pH-Dependency and kinetic parameters were also analyzed using, respectively, buffers at different pHs and varying O-DMT concentrations in the assays.
Of the thirteen human SULTs tested, only SULT1A3 and SULT1C4 were found to display O-DMT-sulfating activity, with different pH-dependency profiles. Kinetic analysis revealed that SULT1C4 was 60 times more catalytically efficient in mediating the sulfation of O-DMT than SULT1A3 at respective optimal pH. Of the four human organ specimens tested, the cytosol prepared from the small intestine showed much higher O-DMT-sulfating activity than cytosols prepared from liver, lung, and kidney. Both cultured HepG2 and Caco-2 cells were shown to be capable of sulfating O-DMT and releasing sulfated O-DMT into cultured media.
SULT1A3 and SULT1C4 were the major SULTs responsible for the sulfation of O-DMT. Collectively, the results obtained provided a molecular basis underlying the sulfation of O-DMT and contributed to a better understanding about the pharmacokinetics and pharmacodynamics of tramadol in humans.
先前的研究表明，硫酸结合参与了曲马多的活性代谢物 O-去甲基曲马多（O-DMT）的代谢。本研究旨在系统地鉴定能够介导 O-DMT 硫酸化的人细胞质硫转移酶（SULT）。
在代谢条件下使用 HepG2 肝癌细胞和 Caco-2 人结肠癌细胞证明了 O-DMT 的硫酸化。使用建立的硫转移酶测定法，检查了 13 种已知的人 SULT 和 4 个人体器官标本对 O-DMT 的硫酸化活性。还分别使用不同 pH 的缓冲液和测定中不同 O-DMT 浓度分析了 pH 依赖性和动力学参数。
在所测试的 13 个人类 SULT 中，仅发现 SULT1A3 和 SULT1C4 具有 O-DMT 硫酸化活性，且具有不同的 pH 依赖性谱。动力学分析表明，在各自的最佳 pH 下，SULT1C4 介导 O-DMT 硫酸化的催化效率比 SULT1A3 高 60 倍。在所测试的 4 个人体器官标本中，从小肠制备的细胞质显示出比从肝、肺和肾制备的细胞质更高的 O-DMT 硫酸化活性。已显示培养的 HepG2 和 Caco-2 细胞能够硫酸化 O-DMT 并将硫酸化的 O-DMT 释放到培养的培养基中。
SULT1A3 和 SULT1C4 是负责 O-DMT 硫酸化的主要 SULT。总的来说，这些结果为 O-DMT 的硫酸化提供了分子基础，并有助于更好地了解曲马多在人体中的药代动力学和药效动力学。
