ENZYMATIC CONVERSION OF HYDROXYETHYLTHIAMINE PYROPHOSPHATE BY BAKER'S YEAST TRANSKETOLASE

The intermediate product of the transketolase reaction is dihydroxyethylthiamine pyrophosphate (DTPP), a glycol aldehyde residue bound to the second carbon atom of the thiazole ring of thiamine pyrophosphate. The aldehyde is subsequently transferred to the acceptor substrate. In the absence of acceptor substrate the reaction is stopped at the stage of DTPP formation. No release of the glycol aldehyde from it occurs. It is shown that apotransketolase can bind hydroxyethylthiamine pyrophosphate, which differs from DTPP by the lack of the hydroxyl group in the aldehyde moiety, and release the hydroxyethyl residue.