This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liang, J Articles by Burris, R H Search for Related Content PubMed PubMed Citation Articles by Liang, J Articles by Burris, R H

research-article

N2O reduction and HD formation by nitrogenase from a nifV mutant of Klebsiella pneumoniae.

Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.

ABSTRACT

Dinitrogenase from a nifV mutant of Klebsiella pneumoniae contains an altered form of iron-molybdenum cofactor (FeMoco) that lacks a biologically active homocitric acid molecule. Change in the composition of FeMoco led to substantial variation in the kinetics of nitrogenase action. The KmS of the mutant enzyme for N2 and N2O were 0.244 and 0.175 atm (24,714 and 17,726 kPa), respectively. The km for N2 was higher and the Km for N2O was lower than that for the wild-type enzyme. The mutant enzyme was ineffective in N2 fixation, in N2O reduction, and in HD formation, as indicated by the low Vmax of these reactions with saturating levels of substrate and under conditions of saturating electron flux. These observations provide further support for the concept that N2, N2O, and D2 interact with the same form of dinitrogenase. H2 evolution by the mutant enzyme is only partially inhibited by CO. Observation that different numbers of electrons are stored in CO-inhibited than in noninhibited dinitrogenase before H2 is released suggests that the mutant enzyme has more sites responsible for H2 evolution than the wild-type enzyme, whose H2 evolution is not inhibited by CO.

This article has been cited by other articles:

• Masukawa, H., Inoue, K., Sakurai, H. (2007). Effects of Disruption of Homocitrate Synthase Genes on Nostoc sp. Strain PCC 7120 Photobiological Hydrogen Production and Nitrogenase. Appl. Environ. Microbiol. 73: 7562-7570 [Abstract] [Full Text]