Seto D, Bhatnagar S K, Bessman M J
McCollum-Pratt Institute, Baltimore, Maryland.
J Biol Chem. 1988 Jan 25;263(3):1494-9.
Deoxyguanosine triphosphate (dGTP) triphosphohydrolase (EC 3.1.5.1) has been purified approximately 16,000-fold to apparent homogeneity from extracts of Escherichia coli. The enzyme has a native molecular weight of 230,000 and a sedimentation coefficient of 9.3 S. Its subunit molecular weight derived from electrophoresis in denaturing polyacrylamide gels is 58,900, and it has a unique N-terminal sequence for the first 25 amino acids, which indicate that the native enzyme is composed of 4 homologous subunits. It is insensitive to sulfhydryl reagents and EDTA and can be heated to 60 degrees C for 60 min without loss of activity. The enzyme requires Mg2+ for activity, is highly specific for dGTP among the canonical deoxynucleoside triphosphates, and has a unique activity among nucleoside triphosphatases in that the products of the reaction are deoxyguanosine and inorganic tripolyphosphate. Preliminary evidence suggest that this enzyme is responsible for the optA mutant phenotype first described by Saito and Richardson (Saito, H., and Richardson, C.C. (1981) J. Virol. 37, 343-351).
三磷酸脱氧鸟苷（dGTP）三磷酸水解酶（EC 3.1.5.1）已从大肠杆菌提取物中纯化至表观均一，纯化倍数约为16,000倍。该酶的天然分子量为230,000，沉降系数为9.3 S。通过在变性聚丙烯酰胺凝胶中电泳得出其亚基分子量为58,900，并且其前25个氨基酸具有独特的N端序列，这表明天然酶由4个同源亚基组成。它对巯基试剂和EDTA不敏感，可加热至60℃ 60分钟而不失活。该酶的活性需要Mg2+，在标准脱氧核苷三磷酸中对dGTP具有高度特异性，并且在核苷三磷酸酶中具有独特的活性，即反应产物是脱氧鸟苷和无机三聚磷酸。初步证据表明，这种酶与Saito和Richardson首次描述的optA突变体表型有关（Saito, H., and Richardson, C.C. (1981) J. Virol. 37, 343 - 351）。
