2.3.1.8 Fe2+ required, Fe2+ or Mn2+, Mn2+ is 50-75% as effective as Fe2+ 487529 2.3.1.8 K+ - 487517, 487521 2.3.1.8 K+ 3.4fold stimulation at 10 mM 487527 2.3.1.8 K+ activates 487515, 487525, 487533, 94495 2.3.1.8 K+ enzyme is activated by low concentrations of NH4+, K+ and Na+, sequence of effectiveness: NH4+, K+, Na+ 487519 2.3.1.8 K+ enzyme is inactive in absence of K+ or NH4+, maximal activation at about 0.02 M 487513 2.3.1.8 K+ K+ or NH4+ at concentration above 10 mM required for maximum activity 487526 2.3.1.8 K+ KCl activates 487525 2.3.1.8 K+ maximum activity in the presence of 20 mM KCl 736033 2.3.1.8 K+ no effect 487524 2.3.1.8 K+ rate of arsenolysis increases with increasing potassium or ammonium salt concentration and reaches a maximum rate at 0.02 to 0.03 M salt concentration 487515 2.3.1.8 KCl stimulates 674792 2.3.1.8 KCl stimulates enzyme activity 2.5-fold 674792 2.3.1.8 Mn2+ required, Fe2+ or Mn2+, Mn2+ is 50-75% as effective as Fe2+ 487529 2.3.1.8 additional information mechanism of activation by univalent cations 487519 2.3.1.8 additional information no activity with: Fe3+, Zn2+, Mg2+, Co2+, Ni2+, Sn2+, Cu2+, Mo6+, K+, NH4+ 487529 2.3.1.8 Na+ less effective than NH4+ and K+ 487519 2.3.1.8 NH4+ - 487517, 94495 2.3.1.8 NH4+ 5.2fold stimulation at 10 mM 487527 2.3.1.8 NH4+ above 10 mM 487526 2.3.1.8 NH4+ activates 487525, 487533 2.3.1.8 NH4+ enzyme is activated by low concentrations of NH4+, K+ and Na+, sequence of effectiveness: NH4+, K+, Na+ 487519 2.3.1.8 NH4+ K+ or NH4+ at concentration above 10 mM required for maximum activity, enzyme is inactive in absence of K+ or NH4+, maximal activation at about 0.02 M 487513 2.3.1.8 NH4+ maximum activity in the presence of 20 mM NH4Cl 736033 2.3.1.8 NH4+ NH4Cl activates 487525 2.3.1.8 NH4+ no effect 487524 2.3.1.8 NH4+ rate of arsenolysis increases with increasing potassium or ammonium salt concentration and reaches a maximum rate at 0.02 to 0.03 M salt concentration 487515 2.3.1.8 NH4+ required for maximum activity, optimum at 7 mM (NH4)2SO4 487514 2.3.1.8 phosphate 1 mM, weak activation 487514 2.3.1.8 Rb+ stimulates 487533 2.3.1.8 Tris maximum activity with Tris buffer, with HEPES and MES catalysis is lowered by ca. 15% 487517