ENZYMATIC CONVERSION OF HYDROXYETHYLTHIAMINE PYROPHOSPHATE BY BAKERS-YEAST TRANSKETOLASE

The intermediate product of the transketolase reaction is dihydroxyeth ylthiamine pyrophosphate (DTPP), a glycol aldehyde residue bound to th e second carbon atom of the thiazole ring of thiamine pyrophosphate. T he 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 pyroph osphate, which differs from DTPP by the lack of the hydroxyl group in the aldehyde moiety, and release the hydroxyethyl residue.