[Purification and properties of a catalytically active fragment of soluble nucleoside triphosphatase from bovine kidney].

A catalytic fragment of soluble NTPase has been isolated from bovine kidneys.The 236-fold purification was carried out to obtain the preparation with a specific activity of 37.7 U/mg of protein. The purification scheme included the enzyme extraction followed by four column chromatography steps. The catalytic fragment was activated with divalent metal ions, had a pH optimum of 7.0, and possessed specificity for ITP, GTP, UTP and XTP. The apparent K(m) for Mg-ITP, Mg-GTP and Mg-UTP complexes were calculated from Hanes plots to be 1.70 mM, 0.93 mM and 0.48 mM, respectively. As estimated by gel filtration and SDS-PAAGE, the catalytic fragment has Mw 54.7 kDa being composed of two identical polypeptide chains. Our results suppose soluble NTPase from bovine kidney to consist of regulatory and catalytic structural units.