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The methionine salvage pathway is universally used to regenerate methio-nine from 5¢-methylthioadenosine, a byproduct of certain reactions involv-ing S-adenosylmethionine. We identified and verified the genes encoding the enzymes of all steps in this cycle in a commonly used eukaryotic model system: the yeast Saccharomyces cerevisiae. | ỊFEBS Journal A complete inventory of all enzymes in the eukaryotic methionine salvage pathway Ivan Pirkov Joakim Norbeck Lena Gustafsson and Eva Albers Department of Chemicaland BiologicalEngineering - Molecular Biotechnology Chalmers University of Technology Goteborg Sweden Keywords 4-methylthio-2-oxobutyrate transaminases 5 -methylthioribulose-1-phosphate dehydratase Mde1p Mri1p Saccharomyces cerevisiae Correspondence E. Albers Department of Chemical and BiologicalEngineering - Molecular Biotechnology Chalmers University of Technology SE-412 96 Goteborg Sweden Fax 46 31 772 3801 Tel 46 31 772 3838 E-mail albers@chalmers.se Received 15 April2008 revised 9 June 2008 accepted 13 June 2008 doi 10.1111 j.1742-4658.2008.06552.x The methionine salvage pathway is universally used to regenerate methionine from 5 -methylthioadenosine a byproduct of certain reactions involving S-adenosylmethionine. We identified and verified the genes encoding the enzymes of all steps in this cycle in a commonly used eukaryotic model system the yeast Saccharomyces cerevisiae. The genes encoding 5 -methyl-thioribose-1-phosphate isomerase and 5 -methylthioribulose-1-phosphate dehydratase are herein named MRI1 and MDE1 respectively. The 5 -meth-ylthioadenosine phosphorylase was verified as Meu1p the 2 3-dioxomethi-opentane-1-phosphate enolase phosphatase as Utr4p and the aci-reductone dioxygenase as Adi1p. The homologue of the enolase phosphatase gene YNL010w was excluded from its candidate role in the cycle. The methodology used involved auxotrophic growth tests and analysis of intracellular 5 -methylthioadenosine in deletion mutants. The last step a transamination of 4-methylthio-2-oxobutyrate to yield methionine was found to be a highly redundant step. It was catalysed by amino acid transaminases mainly coupled with aromatic and branched chain amino acids as amino donors but also with proline lysine and glutamate glutamine. The aromatic amino acid transaminases Aro8p and Aro9p and the .
