PATHWAYS OF NUCLEOTIDE BIOSYNTHESIS IN MYCOPLASMA-MYCOIDES SUBSP MYCOIDES
PATHWAYS OF NUCLEOTIDE BIOSYNTHESIS IN MYCOPLASMA-MYCOIDES SUBSP MYCOIDES
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DOI：
10.1128/jb.130.3.1047-1054.1977
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发表时间：
1977-01-01
影响因子：
3.2
通讯作者：
FINCH, LR
中科院分区：
文献类型：
--
作者：
MITCHELL, A;FINCH, LR
通过测定在不同生长条件下14C标记前体掺入后从RNA中分离的核苷酸的比活性，揭示了丝状支原体核糖核苷酸合成的主要途径。对霉菌进行了定义。丝状支原体不具有核苷酸从头合成的途径，但具有核苷酸相互转化的能力。尿嘧啶提供了这两种嘧啶核糖核苷酸的要求。胸腺嘧啶也是必需的，这表明甲基化步骤是不可用的。胞嘧啶没有任何用处。尿苷被迅速降解为尿嘧啶。胞苷与尿嘧啶有效竞争，提供了大部分胞苷核苷酸，也提供了相当比例的尿苷核苷酸。与这些结果一致的是，在丝状支原体的培养中，胞苷缓慢脱氨为尿苷，并进一步降解为尿嘧啶。鸟嘌呤能够满足机体对嘌呤核苷酸的全部需求，可能是通过中间体IMP将GMP转化为AMP。当与鸟嘌呤一起使用时，腺嘌呤有效地提供了腺嘌呤核苷酸的全部供应，但次黄嘌呤提供了部分供应。腺嘌呤和次黄嘌呤均不能作为鸟嘌呤核苷酸合成的前体。外源鸟苷、肌苷和腺苷被迅速裂解到相应的碱基上，从而显示出与后者相似的利用模式。
By measuring the specific activity of nucleotides isolated from RNA after the incorporation of 14C-labeled precursors under various conditions of growth, the major pathways of ribonucleotide synthesis in M. mycoides sp. mycoides were defined. M. mycoides did not possess pathways for the de novo synthesis of nucleotides but was capable of interconversion of nucleotides. Uracil provided the requirement for both pyrimidine ribonucleotides. Thymine is also required, suggesting that the methylation step is unavailable. No use was made of cytosine. Uridine was rapidly degraded to uracil. Cytidine competed effectively with uracil to provide most of the cytidine nucleotide and also provided an appreciable proportion of uridine nucleotide. In keeping with these results, there was a slow deamination of cytidine to uridine with further degradation to uracil in cultures of M. mycoides. Guanine was capable of meeting the full requirement of the organism for purine nucleotide, presumably by conversion of GMP to AMP via the intermediate IMP. When available with guanine, adenine effectively gave a complete provision of adenine nucleotide, but hypoxanthine gave a partial provision. Neither adenine nor hypoxanthine could act as a precursor for the synthesis of guanine nucleotide. Exogenous guanosine, inosine and adenosine underwent rapid cleavage to the corresponding bases and thus show a pattern of utilization similar to that of the latter.