TAILIEUCHUNG - Báo cáo khoa học: Novel modified version of nonphosphorylated sugar metabolism – an alternative L-rhamnose pathway of Sphingomonas sp.

Several bacteria, including Azotobacter vinelandii, possess an alternative pathway ofl-rhamnose metabolism, which is different from the known bacterial pathway. In a previous article, a gene cluster related to this path-way was identified, consisting of the genes encoding the four metabolic enzymes l-rhamnose-1-dehydrogenase (LRA1), l-rhamnono-c-lactonase (LRA2), | Novel modified version of nonphosphorylated sugar metabolism - an alternative L-rhamnose pathway of Sphingomonas sp. Seiya Watanabe1 2 3 and Keisuke Makino1 2 3 4 1 Institute of Advanced Energy Kyoto University Japan 2 New Energy and IndustrialTechnology Development Organization Gokasho Uji Kyoto Japan 3 CREST Japan Science and Technology Agency Gokasho Uji Kyoto Japan 4 Innovative Collaboration Center Kyoto University Japan Keywords Entner-Doudoroff pathway gene cluster L-rhamnose metabolic evolution Sphingomonas sp. Correspondence S. Watanabe Institute of Advanced Energy Kyoto University Gokasho Uji Kyoto 611-0011 Japan Fax 81 774 38 3524 Tel 81 774 38 3596 E-mail irab@ Received 30 October 2008 revised 9 December 2008 accepted 5 January 2009 doi Several bacteria including Azotobacter vinelandii possess an alternative pathway of L-rhamnose metabolism which is different from the known bacterial pathway. In a previous article a gene cluster related to this pathway was identified consisting of the genes encoding the four metabolic enzymes L-rhamnose-1-dehydrogenase LRA1 L-rhamnono-y-lactonase LRA2 L-rhamnonate dehydratase LRA3 and L-2-keto-3-deoxyrhamno-nate l-KDR aldolase LRA4 by which L-rhamnose is converted into pyruvate and L-lactaldehyde through analogous reaction steps to the well-known Entner-Doudoroff ED pathway. In this study bioinformatic analysis revealed that Sphingomonas sp. possesses a gene cluster consisting of LRA1-3 and two genes of unknown function LRA5 and LRA6. LRA5 catalyzed the NAD -dependent dehydrogenation of several L-2-keto-3-de-oxyacid-sugars including l-KDR. Furthermore the reaction product was converted to pyruvate and L-lactate by LRA6 this is different from the pathway of Azotobacter vinelandii. Therefore LRA5 and LRA6 were assigned as the novel enzymes l-KDR 4-dehydrogenase and L-2 4-diketo-3-deoxyrhamnonate hydrolase respectively. Interestingly both enzymes were phylogenetically .

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