The long term objectives of the research supported by this grant are to determine the novel chemical mechanisms by which vitamin B6 (PLP), Vitamin B12 (adenosylcobalamin), S-adenosylmethionine (SAM), and iron-sulfur clusters function in enzymatic reaction. The conventional role of PLP biology is to stabilize carbanionic intermediates in enzymatic reactions. A major focus of the research supported by this grant is the elucidation of the role of PLP in catalyzing reactions that involve free radical-paramagnetic intermediates. PLP-facilitated radical reactions appear to take place in reactions of aminomutases such as lysine 2,3-aminomutase and lysine 5,6-aminomutase. Radical intermediates of substrates and vitamin coenzymes will be characterized spectroscopically, and the structures of the enzymes that catalyze their reactions will be elucidated. The roles of SAM and [4Fe-4S] clusters in the initiation of radical formation will be unmasked and characterized chemically, spectroscopically, and kinetically. The relationship between the actions of adenosylcobalamin in Vitamin B 12-dependent and SAM/[4Fe-4S]-dependent aminomutases will be explored. Novel chemistry in the actions of vitamins B6 and B12, SAM, and [4Fe-4S] will be discovered. New beta-aminoacids will be produced by engineering of the genes producing aminomutases. Aminomutases are important in amino acid metabolism and the biosynthesis of antibiotics such as Streptothricin F, Myomycin, Blasticidin S, and Taxol. The contributions of beta- amino acids produced by lysine 2,3-aminomutase and arginine 2,3-aminomutase to the functions of antibiotics are not known. The beta-aminoacids may become significant in drug development.
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