广州管圆线虫成虫嘧啶核苷酸生物合成途径

Pathways of pyrimidine nucleotide biosynthesis in gravid Angiostrongylus cantonensis.

作者信息

So N N, Wong P C, Ko R C

机构信息

Department of Biochemistry, University of Hong Kong.

出版信息

Mol Biochem Parasitol. 1993 Jul;60(1):45-51. doi: 10.1016/0166-6851(93)90027-u.

DOI:10.1016/0166-6851(93)90027-u

PMID:8366894

Abstract

The incorporation of radioactive precursors into pyrimidine nucleotides via de novo and salvage pathways was measured in gravid Angiostrongylus cantonensis by HPLC and thin-layer chromatography. 14C-labelled orotate, uridine, uracil and deoxyuridine were traced to UMP, UDP, UTP, UDP-glucose, dTMP, CMP, CDP and CTP. 3H-labelled cytidine was also incorporated into both uracil and cytosine nucleotides in a ratio of 2:1. Cytosine was a major end-product for all the precursors. Cytosine nucleotides were probably formed from UTP by the action of CTP synthetase whose activity in crude cell-free extract was 31.5 +/- 4.9 pmol min-1 (mg protein)-1. It was dependent on glutamine, ATP and GTP and was inhibited by CTP. The total amount of pyrimidine nucleotides formed from uridine was 3 times of that from uracil. The presence of uracil in the metabolism of uridine indicates that UMP is formed by uracil phosphoribosyltransferase as well as by uridine kinase. UMP is a key intermediate for cytidylate and thymidylate biosynthesis in the gravid worms.

摘要

通过高效液相色谱法和薄层色谱法，测定了妊娠状态下的广州管圆线虫中放射性前体通过从头合成途径和补救途径掺入嘧啶核苷酸的情况。14C标记的乳清酸、尿苷、尿嘧啶和脱氧尿苷被追踪到UMP、UDP、UTP、UDP-葡萄糖、dTMP、CMP、CDP和CTP。3H标记的胞苷也以2:1的比例掺入尿嘧啶和胞嘧啶核苷酸中。胞嘧啶是所有前体的主要终产物。胞嘧啶核苷酸可能是由UTP通过CTP合成酶的作用形成的，其在粗制无细胞提取物中的活性为31.5±4.9 pmol min-1（mg蛋白）-1。它依赖于谷氨酰胺、ATP和GTP，并受到CTP的抑制。由尿苷形成的嘧啶核苷酸总量是由尿嘧啶形成的总量的3倍。尿嘧啶在尿苷代谢中的存在表明UMP是由尿嘧啶磷酸核糖基转移酶以及尿苷激酶形成的。UMP是妊娠线虫中胞苷酸和胸苷酸生物合成的关键中间体。