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目的研究扁桃酸(MA)在大鼠、小鼠和兔组织中的立体选择性代谢,探讨MA代谢酶存在的部位、辅酶依赖性等性质以及可能的种属差异。方法MA对映体与大鼠、小鼠和兔的肝脏、肺、肾脏S9和微粒体共孵育,HPLC检测代谢并用柱前衍生化方法进行手性分析。同时考察辅酶NADH和NADPH及醇脱氢酶竞争性底物乙醇和抑制剂4-甲基吡唑对S-MA代谢的影响。结果S-MA在大鼠肝和肾S9中被代谢为PGA,而R-MA无代谢。两对映体在小鼠和兔组织中均不被代谢。乙醇和4-甲基吡唑不影响酶的活性,该代谢顺利进行的重要辅酶是NADPH而非NADH。结论大鼠中参与MA立体选择性代谢的酶是存在于胞浆或线粒体中的具有NADPH依赖性的非微粒体酶,而不是醇脱氢酶。MA的立体选择性代谢存在种属差异性。
Objective To study the stereoselective metabolism of mandelic acid (MA) in rat, mouse and rabbit tissues, and investigate the location of the metabolites of MA and the coenzyme - dependent properties as well as possible species differences. Methods MA enantiomers were co-incubated with rat, mouse and rabbit liver, lung and kidney S9 and microsomes. The metabolites were determined by HPLC and analyzed by precolumn derivatization. The effects of coenzyme NADH, NADPH and NADPH, alcohol and dehydrogenase, a substrate for ethanol synthesis and 4-methylpyrazole, on S-MA metabolism were also investigated. Results S-MA was metabolized to PGA in rat liver and kidney S9, whereas R-MA was not metabolized. Both enantiomers are not metabolized in mouse and rabbit tissues. Ethanol and 4-methylpyrazole do not affect enzyme activity, and the key coenzyme that the metabolism proceeds smoothly is NADPH instead of NADH. CONCLUSIONS: The enzyme involved in the stereoselective metabolism of MA in rats is a NADPH-dependent, non-microsomal enzyme present in the cytoplasm or mitochondria rather than an alcohol dehydrogenase. There is species diversity in stereoselective metabolism of MA.