Isoenzymes of GMP kinase from L1210 cells: Isolation and characterization

Guanylate kinase from a mouse leukemic L1210 cells has been purified nearly to homogeneity for the first time. It consists of five isoenzymes with pi 5.95, 5.50, 5.08, 4.83 and 4.51, respectively. The native enzyme is a monom er with a relative molecular mass 25 000. The kinetic constants K-m, V-max and k(cat)/K-m of isoenzymes were estimated. The purified GMP kinase is abs olutely specific to GMP and/or dGMP as phosphate acceptor but has a broad s pecificity to nucleoside 5'-triphosphates as phosphate donors.