Effect of salts on Azotobacter vinelandii nitrogenase activities. Inhibition of iron chelation and substrate reduction.

摘要: The effect of salts on the catalytic activity molybdenum-containing nitrogenase complex from Azotobacter vinelandii has been investigated. NaCl was found to inhibit reduction substrates, protons, acetylene, and dinitrogen by a common mechanism. pattern inhibition is sigmoidal, indicating highly cooperative interaction involving multiple inhibitor sites. Sixteen other that were investigated also exhibited this inhibition. functions as dead-end without altering number MgATP hydrolyzed/electron transferred substrate. level expressed sensitive concentration, molar ratio MoFe-protein (Av1) Fe-protein (Av2), total protein concentration. In addition, an MgATP-dependent, iron chelation Av2. Although over same salt concentration range for substrate reduction, hyperbolic. A model based upon simple equilibrium interactions among enzyme species, nucleotides, developed which quantitatively accounts observed effects salt. model, formation active between Av1 Av2 abolished salts. Likewise, apparent affinity reduced. An additional prediction independent nucleotide binding.