Chorismic acid, a key metabolite in modification of tRNA.
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Chorismic acid is the common precursor for the biosynthesis of the three aromatic amino acids as well as for four vitamins. Mutants of Escherichia coli defective in any of the genes involved in the synthesis of chorismic acid are also unable to synthesize uridine 5-oxyacetic acid (cmo5U) and its methyl ester (mcmo5U). Both modified nucleosides are normally present in the wobble position of some tRNA species. Mutants defective in any of the specific pathways leading to phenylalanine, tyrosine, tryptophan, folate, enterochelin, ubiquinone, and menaquinone have normal levels of cmo5U and mcmo5U in their tRNA. The presence of shikimic acid in the growth medium restores the ability of an aroD mutant to synthesize cmo5U, while O-succinylbenzoate, which is an early intermediate in the synthesis of menaquinone, does not. Thus, chorismic acid is a key metabolite in the synthesis of these two modified nucleosides in tRNA. The absence of chorismic acid blocks the formation of cmo5U and mcmo5U at the first step, which might be the formation of 5-hydroxyuridine. This results in an unmodified U in the wobble position of tRNA(1Val) and in most of the tRNAs normally containing cmo5U and mcmo5U. Since cmo5U and mcmo5U are synthesized under anaerobic conditions, the formation of these nucleosides does not require molecular oxygen. One of the carbon atoms of the side chain, --O--CH2--COOH, originates from the methyl group of methionine. The other carbon atom does not originate directly from the C-1 pool, from the carboxyl group methionine, or from bicarbonate. This metabolic link between intermediary metabolism and translation also exists for another member of the family Enterobacteriaceae, Salmonella typhimurium, as well as for the distantly related gram-positive organism Bacillus subtilis. (+info)
Biosynthesis of the immunosuppressants FK506, FK520, and rapamycin involves a previously undescribed family of enzymes acting on chorismate.
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Increased glutamine in leaves of poplar transgenic with pine GS1a caused greater anthranilate synthetase alpha-subunit (ASA1) transcript and protein abundances: an auxin-related mechanism for enhanced growth in GS transgenics?
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pH Dependence of catalysis by Pseudomonas aeruginosa isochorismate-pyruvate lyase: implications for transition state stabilization and the role of lysine 42.
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Insight into the transmission biology and species-specific functional capabilities of tsetse (Diptera: glossinidae) obligate symbiont Wigglesworthia.
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Molecular dynamics simulation of the last step of a catalytic cycle: product release from the active site of the enzyme chorismate mutase from Mycobacterium tuberculosis.
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