А. F. Makarchikov
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 Km 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.
Key words: nucleoside triphosphatase, catalytic fragment, molecular weight, kinetic properties.
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