Kinetics for poly-P and ATP synthesizing activities by PPK1 mutants.

Poly-P synthesizing activity was assessed with mPPK1 or different mutants (40 µg/reaction) by using ATP (2–20 mM for Y524A and 0.125–10 mM for others). ATP synthesis activity was monitored by incubating purified mPPK1 or mutants (5 µg/reaction) with different concentrations of ADP (1–12 mM for H510A and 12.5–800 µM for others) in the presence of poly-P20. Km and Vmax values in each case were determined by non-linear regression analysis of Michaelis-Menten equation. kcat values were calculated considering molecular mass of the recombinant mPPK1 as 86 kDa. Results are presented as Mean ± SD (n = 7 for wild-type and 3 for others).anot detectable.