Hirst M, Haliday E, Nakamura J, Lou L
Institute of Biochemistry and Cell Biology, Syntex Discovery Research, Palo Alto, California 94303.
J Biol Chem. 1994 Sep 23;269(38):23830-7.
GMP synthetase is a key enzyme in the de novo synthesis of guanine nucleotides. Human GMP synthetase has been purified to homogeneity, and a cDNA encoding the enzyme has been isolated from the T-lymphoblastoma cell line, A3.01. The open reading frame encodes a protein of 693 amino acids with a predicted molecular weight of 76,725. The cDNA complements a guaA mutant of Escherichia coli, which lacks a functional GMP synthetase and extracts from the transformed E. coli exhibit GMP synthetase activity, which is absent in the parental strain. RNA hybridization analysis shows that human GMP synthetase is encoded by a single 2.4-kilobase message. DNA hybridization analysis suggests that the human GMP synthetase is encoded by one gene. In several human cell lines, the level of mRNA expression is substantially higher in proliferating, transformed cells than in nontransformed cells. In two transformed cell lines, treatment with phorbol ester inhibits proliferation and results in a dramatic down-regulation in the levels of GMP synthetase mRNA and protein.
GMP合成酶是鸟嘌呤核苷酸从头合成中的关键酶。人GMP合成酶已被纯化至同质，并且从T淋巴细胞瘤细胞系A3.01中分离出了编码该酶的cDNA。开放阅读框编码一个由693个氨基酸组成的蛋白质，预测分子量为76,725。该cDNA可互补大肠杆菌的guaA突变体，该突变体缺乏功能性的GMP合成酶，而从转化的大肠杆菌中提取的物质表现出GMP合成酶活性，而亲本菌株中不存在这种活性。RNA杂交分析表明，人GMP合成酶由一条2.4千碱基的信使RNA编码。DNA杂交分析表明，人GMP合成酶由一个基因编码。在几种人类细胞系中，增殖的转化细胞中mRNA表达水平明显高于未转化细胞。在两种转化细胞系中，用佛波酯处理可抑制增殖，并导致GMP合成酶mRNA和蛋白质水平的显著下调。
