中國醫藥大學機構典藏 China Medical University Repository, Taiwan:Item 310903500/34982
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    题名: L-Lysine Catabolism Is Controlled by L-Arginine and ArgR in Pseudomonas aeruginosa PAO1
    作者: (Han Ting Chou);(Mohamed Hegazy);盧仲達(Chung-Dar Lu)*
    贡献者: 醫學檢驗生物技術學系
    关键词: L-Lysine Catabolism;Pseudomonas
    日期: 2010-11
    上传时间: 2010-11-24 16:10:55 (UTC+8)
    摘要: In comparison to other pseudomonads, Pseudomonas aeruginosa grows poorly in L-lysine as a sole source of
    nutrient. In this study, the ldcA gene (lysine decarboxylase A; PA1818), previously identified as a member of the
    ArgR regulon of L-arginine metabolism, was found essential for L-lysine catabolism in this organism. LdcA was
    purified to homogeneity from a recombinant strain of Escherichia coli, and the results of enzyme characterization
    revealed that this pyridoxal-5-phosphate-dependent decarboxylase takes L-lysine, but not L-arginine, as a substrate.
    At an optimal pH of 8.5, cooperative substrate activation by L-lysine was depicted from kinetics studies, with
    calculated Km and Vmax values of 0.73 mM and 2.2 mole/mg/min, respectively. Contrarily, the ldcA promoter was
    induced by exogenous L-arginine but not by L-lysine in the wild-type strain PAO1, and the binding of ArgR to this
    promoter region was demonstrated by electromobility shift assays. This peculiar arginine control on lysine utilization
    was also noted from uptake experiments in which incorporation of radioactively labeled L-lysine was
    enhanced in cells grown in the presence of L-arginine but not L-lysine. Rapid growth on L-lysine was detected in a
    mutant devoid of the main arginine catabolic pathway and with a higher basal level of the intracellular L-arginine
    pool and hence elevated ArgR-responsive regulons, including ldcA. Growth on L-lysine as a nitrogen source can also
    be enhanced when the aruH gene encoding an arginine/lysine:pyruvate transaminase was expressed constitutively
    from plasmids; however, no growth of the ldcA mutant on L-lysine suggests a minor role of this transaminase in
    L-lysine catabolism. In summary, this study reveals a tight connection of lysine catabolism to the arginine regulatory
    network, and the lack of lysine-responsive control on lysine uptake and decarboxylation provides an explanation of
    L-lysine as a poor nutrient for P. aeruginosa.
    關聯: JOURNAL OF BACTERIOLOGY 192(22):5874-5880
    显示于类别:[醫學檢驗生物技術學系暨碩士班 ] 期刊論文

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