Schmidt W, Arnold H H, Kersten H
J Bacteriol. 1977 Jan;129(1):15-21. doi: 10.1128/jb.129.1.15-21.1977.
Trimethoprim, an inhibitor that prevents tetrahydrofolate-dependent transmethylation reactions inbacteria, was used in a comparative study to discriminate between two possible biosynthetic pathways, either the S-adenosylmethionine or the tetrahydrofolate-dependent formation of ribothymidine (rT) in transfer ribonucleic acids (tRNA's) of several strains of gram-positive and gram-negative microorganisms. rT-deficient tRNA's accumulate in trimethoprim-treated gram-positive Streptococcus faecium, Staphylococcus aureus, Corynebacterium bovis, Arthrobacter albidus, and all examined Bacillaceae, except Bacillus stearothermophilus. The rT-deficient rT-deficient tRNA's accept the methyl moiety from S-adenosylmethionine in vitro, with extracts from Escherichia coli (wild type) as a source of methylating enzymes; 90% of the incorporated methyl groups are present in rT. Trimethoprim does not inhibit the biosynthesis of rT in tRNA of gram-negative Enterobacteriaceae, Rhizobium lupini, and Pseudomonadaceae, suggesting that the rT-specific tRNA methyltransferases of these gram-negative strains use S-adenosylmethionine as coenzyme.
甲氧苄啶是一种能抑制细菌中依赖四氢叶酸的转甲基化反应的抑制剂，在一项比较研究中被用于区分两种可能的生物合成途径，即几种革兰氏阳性和革兰氏阴性微生物的转移核糖核酸（tRNA）中，核糖胸苷（rT）是通过S-腺苷甲硫氨酸途径还是依赖四氢叶酸途径形成的。在经甲氧苄啶处理的革兰氏阳性粪肠球菌、金黄色葡萄球菌、牛棒状杆菌、白色节杆菌以及除嗜热脂肪芽孢杆菌外的所有被检测芽孢杆菌科细菌中，缺乏rT的tRNA会积累。体外实验中，以大肠杆菌（野生型）提取物作为甲基化酶来源时，缺乏rT的tRNA能从S-腺苷甲硫氨酸接受甲基部分；掺入的甲基基团90%存在于rT中。甲氧苄啶不抑制革兰氏阴性肠杆菌科、羽扇豆根瘤菌和假单胞菌科细菌tRNA中rT的生物合成，这表明这些革兰氏阴性菌株的rT特异性tRNA甲基转移酶以S-腺苷甲硫氨酸作为辅酶。
