Sivuk V F, Rusina I M, Makarchikov A F
Laboratory of Biochemical Toxicology and Narcology, Institute of Pharmacology and Biochemistry, National Academy of Sciences of Belarus, Grodno, 230030, Belarus.
Biochemistry (Mosc). 2008 Sep;73(9):1047-52. doi: 10.1134/s0006297908090137.
Soluble NTPase, differing in its properties from known proteins exhibiting NTPase activity, was purified from bovine brain to homogeneity. The enzyme has pH optimum at 7.5 and shows absolute dependence on bivalent cations and broad substrate specificity towards nucleoside-5 -tri- and -diphosphates, characteristics of apyrases. The NTPase follows Michaelis-Menten kinetics in the range of investigated substrate concentrations, the apparent K(m) values for UTP, ITP, GTP, CTP, CDP, and ATP being 86, 25, 41, 150, 500, and 260 microM, respectively. According to gel-filtration and SDS-PAGE data, the molecular mass of the enzyme is 60 kD. The NTPase is localized in the cytosol fraction and expressed in different bovine organs and tissues. Total NTPase activity of extracts of bovine organs and tissues decreases in the following order: liver > heart > skeletal muscle > lung > brain > spleen > kidney ~ small intestine. The enzyme activity can be regulated by acetyl-CoA, alpha-ketoglutarate, and fructose-1,6-diphosphate acting as activators in physiological concentrations, whereas propionate exhibits an inhibitory effect.
从牛脑中纯化出了一种可溶性NTP酶，其性质与已知具有NTP酶活性的蛋白质不同，达到了同质纯品。该酶的最适pH值为7.5，对二价阳离子表现出绝对依赖性，对核苷-5'-三磷酸和二磷酸具有广泛的底物特异性，这些都是腺苷三磷酸双磷酸酶的特征。在所研究的底物浓度范围内，该NTP酶遵循米氏动力学，UTP、ITP、GTP、CTP、CDP和ATP的表观K(m)值分别为86、25、41、150、500和260 microM。根据凝胶过滤和SDS-PAGE数据，该酶的分子量为60 kD。该NTP酶定位于胞质溶胶部分，在牛的不同器官和组织中表达。牛器官和组织提取物的总NTP酶活性按以下顺序降低：肝脏>心脏>骨骼肌>肺>脑>脾脏>肾脏~小肠。该酶的活性可受到生理浓度下作为激活剂的乙酰辅酶A、α-酮戊二酸和果糖-1,6-二磷酸的调节，而丙酸盐则表现出抑制作用。
