Nitrogenase of Klebsiella pneumoniae. Inhibition of acetylene reduction by magnesium ion explained by the formation of an inactive dimagnesium–adenosine triphosphate complex

[摘要]

Acetylene-reducing activity of purified nitrogenase from Klebsiella pneumoniae was studied over a range of ATP and Mg²⁺ concentrations at 15°C, pH7.8. Inhibition at Mg²⁺ concentrations of 2.5–30mm was due to the formation of the inactive complex, Mg₂ATP. At higher Mg²⁺ concentrations an additional inhibitory effect was observed. The results were consistent with a MgATP complex being the active substrate with an apparent K_m(MgATP)=0.4mm.