The long term objective is to elucidate the mechanisms by which binding energy facilitates enzymatic catalysis. A global approach will be adopted in studies of four enzymes that participate in carbohydrate and amino acid metabolism and phosphotransfer, UDP-galactose 4-epimerase (epimerase-NAD+), dTDP-glucose 4,6-dehydratase (dehydratase-NAD), ornithine cyclase (cyclase-NAD+), and human Fhit, a putative tumor suppressor. Chemical, kinetic, spectroscopic, mutagenic, and crystallographic methods will be employed. Carbohydrate metabolism is essential in all living cells and presents fundamental questions bearing on binding energy and catalysis. Cells must break down carbohydrates as energy sources and must produce specific carbohydrates, such as galactose for glycoconjugates. One manifestation of the importance of galactose metabolism is the metabolic defect underlying galactosemia, in which galactose metabolism is impaired by defects in enzymes. The objective in studies of epimerase will be to elucidate the molecular basis for the enhancement of the chemical reactivity of the niacin-coenzyme NAD+ by the use of binding energy between substrates and the enzyme. The structural basis for a charge-transfer interaction between NAD+ and the enzyme will be determined. Research on dehydratase-NAD+ will contrast its biological mechanism with that of epimerase-NAD+. The objectives for cyclase-NAD+ research include the elucidation of the chemical mechanism in the cyclization of ornithine into proline. Research on Fhit is directed toward elucidating its chemical reaction mechanism and the chemical basis for its activity as a tumor suppressor and its mechanistic relationships with galactose-1-P uridylyltransferase. ? ?
| McCoy, Jason G; Arabshahi, Abolfazl; Bitto, Eduard et al. (2006) Structure and mechanism of an ADP-glucose phosphorylase from Arabidopsis thaliana. Biochemistry 45:3154-62 |
