Arginine and Citrulline Catabolic Pathways Encoded by the arc Gene Cluster of Lactobacillus brevis ATCC 367

Abstract

High concentrations of l-arginine or l-citrulline in the growth medium provided the wine bacterium with a significant growth advantage. The arginine deiminase pathway (ADI) gene cluster of contains three genes-, , and-encoding putative l-arginine/l-ornithine exchangers. Uptake experiments with cells expressing the genes showed that all three transported l-ornithine with affinities in the micromolar range. Similarly, ArcD and ArcE2 transported l-arginine, while ArcE1 transported l-citrulline, an intermediate of the ADI pathway. Chase experiments showed very efficient exchange of l-arginine and l-ornithine by ArcD and ArcE2 and of l-citrulline and l-ornithine by ArcE1. Low affinities (millimolar range) combined with low translocation rates were found for ArcD and ArcE2 with l-citrulline and for ArcE1 with l-arginine. Resting cells of grown in the presence of l-arginine and l-citrulline rapidly consumed l-arginine and l-citrulline, respectively, while producing ammonia and l-ornithine. About 10% of l-arginine degraded was excreted by the cells as l-citrulline. Degradation of l-arginine and l-citrulline was not subject to carbon catabolite repression by glucose in the medium. At a high medium pH, l-citrulline in the medium was required for induction of the l-citrulline degradation pathway. Pathways are proposed for the catabolic breakdown of l-arginine and l-citrulline that merge at the level of ornithine transcarbamylase in the ADI pathway. l-Arginine uptake is catalyzed by ArcD and/or ArcE2, l-citrulline by ArcE1. l-Citrulline excretion during l-arginine breakdown is proposed to be catalyzed by ArcD and/or ArcE2 through l-arginine/l-citrulline exchange., a bacterium isolated from wine, as well as other food environments, expresses a catabolic pathway for the breakdown of l-citrulline in the medium that consists of the l-citrulline/l-ornithine exchanger ArcE1 and part of the catabolic arginine deiminase (ADI) pathway enzymes. The proposed pathways for l-arginine and l-citrulline breakdown provide a mechanism for l-citrulline accumulation in fermented food products that is the precursor of the carcinogen ethyl carbamate.

Characterization of Arginine Catabolism by Lactic Acid Bacteria Isolated from Kimchi

“…Aas also serve as an energy source for bacteria. For example, many lactic acid bacteria use arginine and citrulline as an energy source via the ADI system [ 22 ].…”

“…The ADI pathway comprises arginine deiminase (ADI, arcA ), ornithine transcarboxylase (OTC, arcB ), and carbamate kinase (CK, arcC ). ADI converts l -arginine into l -ornithine and yields 1 mol of ATP per mol of arginine [ 22 ]. ADI converts arginine into citrulline and ammonia.…”

“…CK yields carbon dioxide, ammonia, and ATP [ 23 ]. The arginine to ornithine antiport ( arcD ) system is essential for recycling arginine and citrulline during energy generation [ 22 ].…”

“…Arginine catabolism-related genes include adi , which is required for disassociation of arginine into citrulline and ammonia. The arginine- and citrulline-catabolism pathways of L. brevis have been reported recently [ 22 ]. The ADI pathway comprises a cluster of three genes ( arcD1 , arcE1 , and arcE2 ) [ 22 ].…”

“…The arginine- and citrulline-catabolism pathways of L. brevis have been reported recently [ 22 ]. The ADI pathway comprises a cluster of three genes ( arcD1 , arcE1 , and arcE2 ) [ 22 ]. Arginine facilitates the growth of L. brevis , especially during wine fermentation.…”