Helicobacter pyloriutilises urea for amino acid synthesis

Williams, C.L., Preston, T. , Hossack, M., Slater, C. and McColl, K.E.L. (1996) Helicobacter pyloriutilises urea for amino acid synthesis. FEMS Immunology and Medical Microbiology, 13(1), pp. 87-94. (doi:10.1111/j.1574-695X.1996.tb00220.x)

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Publisher's URL: http://dx.doi.org/10.1111/j.1574-695X.1996.tb00220.x


<i>Helicobacter pylori</i> has one of the highest urease activities of all known bacteria. Its enzymatic production of ammonia protects the organism from acid damage by gastric juice. The possibility that the urease activity allows the bacterium to utilise urea as a nitrogen source for the synthesis of amino acids was investigated. <i>H. Pylori</i> (NCTC 11638) was incubated with 50 mM urea, enriched to 5 atom% excess <sup>15</sup>N, that is the excess enrichment of <sup>15</sup>N above the normal background, in the presence of either NaCl pH 6.0, or 0.2M citrate pH 6.0. <i>E. Coli</i> (NCTC 9001) was used as a urease-negative control. 15N enrichment was detected by isotope ratio mass spectrometry. <i>H. Pylori</i> showed intracellular incorporation of <sup>15</sup>N in the presence of citrate buffer pH 6.0 but there was no significant incorporation of <sup>15</sup>N in unbuffered saline or by <i>E. Coli</i> in either pH 6.0 citrate buffer or unbuffered saline. The intracellular fate of the urea-nitrogen was determined by means of gas chromatography/mass spectrometry following incubation with <sup>15</sup>N enriched 5 mM urea in the presence of either 0.2 M citrate buffer pH 6.0 or 0.2 M acetate buffer pH 6.0. After 5 min incubation in either buffer the <sup>15</sup>n label appeared in glutamate, glutamine, phenylalanine, aspartate and alanine. It appears, therefore, that at pH and urea concentrations typical of the gastric mucosal surface, <i>H. Pylori</i>utilises exogenous urea as a nitrogen source for amino acid synthesis. The ammonia produced by <i>H. Pylori</i> urease activity thus facilitates the organism's nitrogen metabolism at neutral pH as well as protecting it from acid damage at low pH.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Preston, Professor Tom
Authors: Williams, C.L., Preston, T., Hossack, M., Slater, C., and McColl, K.E.L.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:FEMS Immunology and Medical Microbiology
ISSN (Online):1574-695X
Published Online:17 January 2006

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