Open AccessKinetic Studies on Klebsiella pneumoniae Nitrogenase
Author(s) -
R. A. Parejko,
P. W. Wilson
Publication year - 1971
Publication title -
proceedings of the national academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.68.9.2016
Subject(s) - azotobacter vinelandii , nitrogenase , klebsiella pneumoniae , azide , cyanide , azotobacter , chemistry , substrate (aquarium) , enzyme , stereochemistry , biochemistry , non competitive inhibition , bacteria , biology , nitrogen fixation , inorganic chemistry , organic chemistry , escherichia coli , ecology , genetics , nitrogen , gene
Purified cell-free extracts of Klebsiella pneumoniae reduce N(2), N(3) (-), CN(-), or C(2)H(2) in the absence of an ATP-generating system when substrate concentrations of ATP are used. The optimum Mg(++)/ATP ratio is 0.5. Michaelis constants for the reduction of substrates calculated from kinetic studies of K. pneumoniae nitrogenase were similar to those that have been reported for Azotobacter vinelandii and Clostridium pasteurianum. Hill plots of the kinetic data are consistent with the view that there is a single binding site for each of the substrates N(2), C(2)H(2), CN(-), N(3) (-), and ATP. Inhibition studies of K. pneumoniae nitrogenase indicate that ADP competitively inhibits C(2)H(2) reduction. Also, the reducible substrates, N(3) (-) and CN(-), inhibit C(2)H(2) reduction. The inhibition by azide is noncompetitive, that by cyanide is mixed.
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