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Nitrogenase reactivity: azide reduction

Rubinson, J.F., Burgess, B.K., Corbin, J.L. and Dilworth, M.J. (1985) Nitrogenase reactivity: azide reduction. Biochemistry, 24 (2). pp. 273-283.

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We have examined the reduction of azide by the purified component proteins of nitrogenase (Avl and Av2). One of the two species present in azide solutions, HN3, was shown to be a potent substrate (Km =12 μM) which is reduced by six electrons to N2H4 + NH3. HN3 reduction does not yield any less highly reduced products, which implies the presence of tightly bound intermediates. HN3 appears to be an effective inhibitor of H2 evolution and to bind to a redox state of the enzyme more oxidized than that responsible for N2 fixation or H2 evolution. The other species present in solution, N3-, was shown to be the substrate reduced by two electrons to yield N2 + NH3. N3- is the only known anionic nitrogenase substrate, and its reduction is the only example of a nitrogenase reaction requiring inequivalent numbers of protons and electrons. Infinite [N3-] cannot eliminate H2 evolution, and N3- may bind to and be reduced by both high and low redox states of the enzyme. Some of the N2 formed appears to be further reduced by six electrons to two NH3 in a reaction that is inhibited by D2. The N2 formed from N3- reduction, which is subsequently reduced to 2NH3, is not in equilibrium with N2 in the gas phase. This suggests strongly that the N2 must be formed at or near the N2 reduction site.

Item Type: Journal Article
Murdoch Affiliation(s): School of Environmental and Life Sciences
Publisher: ACS Publications
Copyright: © 1985 American Chemical Society.
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