Tatum C M, Benkovic P A, Benkovic S J, Potts R, Schleicher E, Floss H G
Biochemistry. 1977 Mar 22;16(6):1093-102. doi: 10.1021/bi00625a010.
The stereochemistry of the transfer catalyzed by rabbit liver serine transhydroxymethylase (EC 2.1.2.1) of the prochiral hydroxymethyl group from serine to tetrahydrofolate to form 5,10-methylenetetrahydrofolate was studied. Initial kinetic studies on labeled 5,10-methylenetetrahydrofolate showed that nonenzymatic racemization of the prochiral methylene center was buffer dependent and was slow under the conditions employed. Specifically tritiated (3R)- and (3S)-serines were employed to study the transfer reaction. Reactions were carried out under various conditions and the stereochemistry of the methylene carbon of the 5,10-methylenetetrahydrofolate produced was determined. The enzyme was shown to be partially stereospecific for this transfer reaction, proceeding with a loss of about 50% of the stereochemical purity of the transferred carbon center. Possible mechanistic interpretations of this finding are discussed.
研究了兔肝丝氨酸转羟甲基酶（EC 2.1.2.1）催化的前手性羟甲基从丝氨酸转移至四氢叶酸以形成5,10-亚甲基四氢叶酸的立体化学。对标记的5,10-亚甲基四氢叶酸进行的初始动力学研究表明，前手性亚甲基中心的非酶消旋作用取决于缓冲液，在所采用的条件下较慢。具体而言，使用了氚化的（3R）-和（3S）-丝氨酸来研究转移反应。在各种条件下进行反应，并确定所产生的5,10-亚甲基四氢叶酸的亚甲基碳的立体化学。结果表明，该酶对这种转移反应具有部分立体特异性，转移的碳中心的立体化学纯度损失约50%。讨论了这一发现可能的机理解释。
