Oxidation of -ketoaldehyde by thiamine and hydride acceptor. A chemical model for a new role of thiamine in the -ketoaldehyde metabolism.

An adduct of phenylglyoxal with thiamine was readily converted to phenylglyoxylate and thiamine by the action of organic hydride acceptors such as 2, 6-dichlorophenol indophenol, trityl cation, 2-methyl-3-benzylidene-indolenium salt and N-methylnicotinamide. Similar hydride transfer reaction was observed for the adduct of methylglyoxal with thiamine. Direct conversion of phenylglyoxal to phenylglyoxylate by 2, 6-dichlorophenol indophenol was found to occur in the presence of TPP and base. The results indicate a new catalytic role for thiamine in the conversion of α-ketoaldehyde to α-ketoacid.