2.7.1.29 D109A inactive 723640 2.7.1.29 D109N inactive 723640 2.7.1.29 E526K based on the use of hybrid quantum mechanics/molecular mechanics (QM/MM) potentials, with the QM region described by semiempirical and DFT methods, the reaction mechanism of the wild-type enzyme and the most active experimentally measured mutant (Glu526Lys) with polyphosphate as phosphoryl donor is explored to elucidate the origin of the activity of this mutant. The mutation favors a more adequate position of the polyphosphate in the active site for the following step, the chemical reaction, to take place. Structure-function analysis, overview 759376 2.7.1.29 E526K the mutant shows activity with polyphosphate -, 738418 2.7.1.29 H128A inactive 723640 2.7.1.29 H128K inactive 723640 2.7.1.29 H169A completely inactive 641271 2.7.1.29 H439A completely inactive 641271 2.7.1.29 H56A the mutant shows severely reduced catalytic efficiency compared to the wild type enzyme 723640 2.7.1.29 H56N the mutant shows severely reduced catalytic efficiency compared to the wild type enzyme 723640