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R A Parejko

Publications and source records attributed to R A Parejko.

5 recordsLinked to original sources
PubMed1971

Kinetic studies on Klebsiella pneumoniae nitrogenase.

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.

Acetylene↗
PubMed1968

Taxonomy of Azotomonas species.

The ability of two strains of Azotomonas insolita and one strain classified only as Azotomonas species to use molecular nitrogen was investigated by use of several techniques. Molecular (15)N(2) incorporation by growing cultures of Azotomonas was inconsistent and limited. In addition, attempts to demonstrate nitrogen fixation in growing cultures by the radioactive (13)N(2) technique were negative. Experiments were done in which the total nitrogen content of a culture was determined by a micro-Kjeldahl method. None of these experiments resulted in a significant increase in total nitrogen. Attempts to show a diauxie effect, that is, transition from growth on NH(4) (+) to N(2), were also unsuccessful. Nitrogen fixation by cell-free extracts of A. insolita was negative, as determined by reduction of N(2) to NH(3), and reduction of cyanide, of acetylene, and of azide. These negative results suggest that the taxonomic reclassification of the genus Azotomonas should be considered.

Bacteria↗