Polyphosphate kinase (PPK2), a potent, polyphosphate-driven generator of GTP

An enzyme that uses inorganic polyphosphate (poly P) as a donor to convert GDP to GTP has been purified 1,300-fold to homogeneity from lysates of Pseudomonas aeruginosa PAOM5. Poly P chains of 30–50 residues are optimal; those of 15–700 residues can also serve. GDP is preferred over ADP among nucleoside diphosphate acceptors. This nucleoside diphosphate kinase (NDK) activity resides in the same protein isolated for its synthesis of poly P from GTP and designated PPK2 in an accompanying report. The reaction that synthesizes poly P and the reaction that utilizes poly P differ in their kinetic features. Especially notable is the catalytic potency of the NDK activity, which is 75-fold greater than that of poly P synthesis. PPK2 appears in the stationary phase of growth and reaches NDK levels of 5–10% that of the classic NDK; both kinase activities may figure in the generation of the guanosine precursors in the synthesis of alginate, an exopolysaccharide essential for the virulence of P. aeruginosa.