XXXX @entity5688 kinase: purification and characterization.

@entity3007 @entity5688 @entity3208 @entity93 @entity856 @entity5132 @entity3006 @entity1391 @entity2975 @entity855
Soluble @entity5688 kinase (NDP kinase) from @entity5132 was purified to electrophoretic homogeneity and a partial sequence was determined. The enzyme was kinetically and physically characterized. @entity3208 - @entity2975 gel electrophoresis of the purified enzyme revealed a single polypeptide of 17 kDa upon staining, by immunodetection with heterologous and homologous antibodies, and by autoradiography of the phosphorylated enzyme. Furthermore, isoelectric focusing of the purified native enzyme showed a single acidic band (pI 4.5). These results together with a native molecular mass of 98 kDa suggest a hexameric native enzyme composed of identical subunits. Like NDP kinases from other sources, the catalysis involves a phosphoenzyme intermediate that is rapidly formed upon incubation of the enzyme with @entity855 . The transfer of @entity1391 from phosphoprotein intermediate to @entity5688 is equally fast. Kinetic experiments indicated that @entity3007 and @entity855 had the lowest Km compared to @entity856 , dTTP, and @entity93 . @entity3006 acted as a preferred acceptor as assessed by kinetic measurements as well as by competition experiments. Experimental data are presented indicating the existence of a membrane-associated NDP kinase. Preliminary characterization of this enzyme suggests that cytosolic and membrane-associated NDP kinases are similar proteins.
