Kinetic evaluation, using 13N, reveals two assimilatory nitrate transport systems in Klebsiella pneumoniae.

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Abstract
A kinetic evaluation of initial rates of nitrate transport at concentrations between 1 .mu.M and 1 mM indicated the presence of 2 transport processes in K. pneumoniae. Analysis of the contribution of each process to the total activity permitted the determination of kinetic constants (Km) of 4.9 .mu.M and 4.2 mM for the high- and low-affinity systems, respectively. The ratio of the Vmax of the high-affinity system to that of an apparent low-affinity system was about 0.3. Both systems were inhibited by the presence of NH4+ in the transport assay. Growth in the presence of equimolar NO3- and NH4+ repressed the synthesis of both systems when compared with growth in NO3- alone.

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