Chen Y R, Datta N, Roux S J
J Biol Chem. 1987 Aug 5;262(22):10689-94.
A nucleoside triphosphatase/deoxynucleoside triphosphatase associated with the chromatin fraction from a highly purified preparation of pea nuclei has been isolated and characterized. The purified enzyme has a molecular weight of 47,000 as checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and it has an isoelectric point of 6.6. In the presence of divalent cations (Mg2+ = Mn2+ greater than Ca2+), this enzyme hydrolyzes nucleoside triphosphates or deoxynucleoside triphosphates. Hydrolysis is optimal at pH 7.5 and is significantly inhibited by relatively low concentrations of quercetin, but is not sensitive to vanadate, nitrate, or oligomycin. The enzyme has a rather broad nucleotide substrate specificity and has a Km for MgATP2- of 0.6 mM. The enzyme activity is stimulated over 3-fold by Ca2+ and calmodulin, and the stimulation is blocked by the Ca2+ chelator EGTA and by the calmodulin antagonists compound 48/80 and chlorpromazine.
已从高度纯化的豌豆细胞核制剂中分离并鉴定出一种与染色质部分相关的核苷三磷酸酶/脱氧核苷三磷酸酶。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳检测，纯化后的酶分子量为47,000，其等电点为6.6。在二价阳离子（Mg2+ = Mn2+ > Ca2+）存在的情况下，该酶可水解核苷三磷酸或脱氧核苷三磷酸。水解作用在pH 7.5时最为适宜，相对低浓度的槲皮素可显著抑制水解，但该酶对钒酸盐、硝酸盐或寡霉素不敏感。该酶具有相当广泛的核苷酸底物特异性，对MgATP2-的Km值为0.6 mM。Ca2+和钙调蛋白可使酶活性提高3倍以上，而Ca2+螯合剂EGTA以及钙调蛋白拮抗剂化合物48/80和氯丙嗪可阻断这种激活作用。
