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J. Biol. Chem., Vol. 278, Issue 42, 40527-40533, October 17, 2003

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Arginine Metabolism in the Deep Sea Tube Worm Riftia pachyptila and Its Bacterial Endosymbiont^*

Zoran Minic   and Guy Hervé  ¶

From the Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, UMR 7631, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, 96 Boulevard Raspail, F-75006 Paris, France

The present study describes the distribution and properties of enzymes involved in arginine metabolism in Riftia pachyptila, a tubeworm living around deep sea hydrothermal vents and known to be engaged in a highly specific symbiotic association with a bacterium. The results obtained show that the arginine biosynthetic enzymes, carbamyl phosphate synthetase, ornithine transcarbamylase, and argininosuccinate synthetase are present in all of the tissues of the worm and in the bacteria. Thus, Riftia and its bacterial endosymbiont can assimilate nitrogen and carbon via this arginine biosynthetic pathway. The kinetic properties of ornithine transcarbamylase strongly suggest that neither Riftia nor the bacteria possess the catabolic form of this enzyme belonging to the arginine deiminase pathway, the absence of this pathway being confirmed by the lack of arginine deiminase activity. Arginine decarboxylase and ornithine decarboxylase are involved in the biosynthesis of polyamines such as putrescine and agmatine. These activities are present in the trophosome, the symbiont-harboring tissue, and are higher in the isolated bacteria than in the trophosome, indicating that these enzymes are of bacterial origin. This finding indicates that Riftia is dependent on its bacterial endosymbiont for the biosynthesis of polyamines that are important for its metabolism and physiology. These results emphasize a particular organization of the arginine metabolism and the exchanges of metabolites between the two partners of this symbiosis.

Received for publication, July 20, 2003

^* This work was supported by the Centre National de la Recherche Scientifique, l'Université Pierre et Marie Curie and a grant from the program GEOMEX from Centre National de la Recherche Scientifique. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Present address: Biologie cellulaire, Institut National de la Recherche Agronomique, Route de Saint Cyr, 78026 Versailles Cedex, France.

^¶ To whom correspondence should be addressed. Tel.: 33-1-43-53-40-70; Fax: 33-1-42-22-13-98; E-mail: gherve{at}ccr.jussieu.fr.

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