This application describes a program of research designed to investigate the chemistry of biologically important keto-enol systems using the new methods which we have recently developed for examining simple unstable enols in aqueous solution. Three different enols and related substances would be studied: (1) triosephosphate enediol, (2) enolpyruvate, and (3) the enol of acetyl coenzyme A. These enols would be generated flash photolytically by photooxidation-reduction and Norrish type Ii photoelimination as well as thermally by hydrolysis of silyl enol ethers and potassium enolate salts, and rates of their ketonization reactions as well as rates of enolization of the carbonyl isomers would be measured. This would provide basic information, such as keto-enol equilibrium constants and acidity constants of the enols and their keto isomers, which would be helpful in understanding the functions and modes of action of these biologically important molecules. For example, further insight would gained into the mechanism of conversion of dihydroxyacetone phosphate into gyceraldehyde-3-phosphate through catalysis by triosephosphate isomerase, which is a critical step in the glycolytic pathway. The proposed research would also show just how much of the high energy content of phosphoenolpyruvate resides in its masked enol function, and it would elucidate the advantage that thiol esters such as acetyl coenzyme A have over oxygen esters in promoting biological reactions.
