Lo H S, Wang C C
J Parasitol. 1985 Oct;71(5):662-9.
Pulse-labeling of the nucleotide pool in Entamoeba histolytica with radioactive precursors, and subsequent high performance liquid chromatographic (HPLC) analysis of the radiolabeled nucleotides, indicate that E. histolytica is incapable of de novo synthesis of purine nucleotides. Hypoxanthine, inosine and xanthine could not be converted to nucleotides in E. histolytica, which suggests the absence of interconversion between adenine nucleotides and guanine nucleotides through formation of IMP. Adenosine was actively incorporated into nucleotides at an initial rate of 130 pmoles per minute per 10(6) trophozoites. Adenine, guanosine and guanine were also incorporated at much lower rates. The rate of adenine incorporation was enhanced by the presence of guanosine; the rate of guanine incorporation was significantly increased by adenosine. These stimulatory effects suggest that the ribose moiety of adenosine or guanosine can be transferred to another purine base to form a new nucleoside, and that the purine nucleosides are the immediate precursors of E. histolytica nucleotides. HPLC results showed that the radiolabel in adenine was exclusively incorporated into adenine nucleotides and that guanine was found only among guanine nucleotides, whereas the radioactivity associated with the ribose moiety of adenosine or guanosine was distributed among both adenine and guanine nucleotides.
用放射性前体对溶组织内阿米巴的核苷酸库进行脉冲标记，随后对放射性标记的核苷酸进行高效液相色谱（HPLC）分析，结果表明溶组织内阿米巴无法从头合成嘌呤核苷酸。次黄嘌呤、肌苷和黄嘌呤在溶组织内阿米巴中不能转化为核苷酸，这表明腺嘌呤核苷酸和鸟嘌呤核苷酸之间不存在通过形成肌苷酸（IMP）的相互转化。腺苷以每分钟每10⁶个滋养体130皮摩尔的初始速率被积极掺入核苷酸中。腺嘌呤、鸟苷和鸟嘌呤的掺入速率也低得多。鸟苷的存在提高了腺嘌呤的掺入速率；腺苷显著提高了鸟嘌呤的掺入速率。这些刺激作用表明腺苷或鸟苷的核糖部分可以转移到另一个嘌呤碱基上形成新的核苷，并且嘌呤核苷是溶组织内阿米巴核苷酸的直接前体。HPLC结果显示，腺嘌呤中的放射性标记仅掺入腺嘌呤核苷酸中，而鸟嘌呤仅存在于鸟嘌呤核苷酸中，而与腺苷或鸟苷的核糖部分相关的放射性则分布在腺嘌呤和鸟嘌呤核苷酸中。
