Transport of Aromatic Amino Acids by Pseudomonas aeruginosa

Abstract

Kinetic studies of the transport of aromatic amino acids by Pseudomonas aeruginosa revealed the existence of two high-affinity transport systems which recognized the three aromatic amino acids. From competition data and studies on the exchange of preformed aromatic amino acid pools, the first transport system was found to be functional with phenylalanine, tyrosine, and tryptophan (in order of decreasing activity), whereas the second system was active with tryptophan, phenylalanine, and tyrosine. The two systems also transported a number of aromatic amino acid analogues but not other amino acids. Mutants defective in each of the two and in both transport systems were isolated and described. When the amino acids were added at low external concentrations to cells growing logarithmically in glucose minimal medium, the tryptophan pool very quickly became saturated. Under identical conditions, phenylalanine and tyrosine each accumulated in the intracellular pool of P. aeruginosa at a concentration which was 10 times greater than that of tryptophan.

Aromatic amino acid transport in Yersinia pestis

“…The fluoro analogues of phenylalanine were effective inhibitors of phenylalanine and tyrosine transport, indicating that the fluorine atom does not appreciably alter the phenylalanine molecule with respect to recognition by the transport system. This finding is in agreement with studies on the inhibition of phenylalanine transport by fluoro analogues in Salmonella typhimrium (1) and inhibition of tyrosine transport in P. aeruginosa by the fluoro derivatives of tyrosine and phenylalanine (7).…”

“…Tyrosine transport did not show the same degree of stereo specificity as phenylalanine and tryptophan transport since tyrosine transport was inhibited significantly by each of the D aromatic amino acids. These findings are similar to those made for tyrosine transport in P. aeruginosa (7), where Dphenylalanine and D-tyrosine inhibited the transport of L-tyrosine.…”

“…The properties of aromatic amino acid transport in some gram-negative species of bacteria have been characterized. Studies on Salmonella typhimurium (1), Pseudomonas aeruginosa (7), and Escherichia coli K-12 (4, 5) have revealed enzyme-like, active transport systems for the uptake of aromatic amino acids. Kinetic studies and cross competition and exchange experiments have further shown the presence of multiple transport systems in each species.…”

“…S. typhimurium (1) and E. coli K-12 (4) possess general systems, which show equal transport activity for any one of the aromatic amino acids, and specific systems which have greatest specificity and transport activity for individual aromatic amino acids. P. aeruginosa has two transport systems, designated transport system I and II, ' Present address: Division of Neurology, Duke University Medical Center, Durham, N.C. 27710. which are functional with phenylalanine, tyrosine, and tryptophan (I) and tryptophan, phenylalanine, and tyrosine (II) (7). Division of aromatic amino acid transport systems has been further clarified by the isolation of mutants defective in transport over a designated system.…”

Variation in transport explains polymorphism of histidine and urocanate utilization in a natural Pseudomonas population

“…The rates reported here for histidine transport, while comparable to those reported for amino acid transport in whole cells of P. aeruginosa (Kay and Gronlund, 1969;1971), are lower than the rate of amino acid consumption required for growth. To determine if this was unique to histidine with P. fluorescens SBW25, we measured the transport of both [ 3 H]-and [ 14 C]-labelled amino acids at a final concentration of 5 mM.…”