The effect of acetaldehyde on human brain transketolase activity

Chronic alcoholism and thiamine deficiency are well documented factors in the aetiology of Wernicke‐Korsakoff Syndrome. More recently, acetaldehyde (ACH) has been implicated as a possible aetiological factor. In the present investigation the direct effect of ACH was studied on the activity of transketolase, a thiaminedependent enzyme, as well as two non‐thiamine‐dependent enzymes (aspartate aminotransferase and lactate dehydrogenase), isolated from five control human brains. The concentration of ACH required to inhibit 50% activity of holo‐ and apo‐transketolase was 80 mM and 60 mM, respectively, whereas that for aspartate aminotransferase and lactate dehydrogenase was 14 mM and 10 mM, respectively. None of the enzymes were completely inhibited by the range of ACH concentrations used in the study. It was concluded that the thiamineindependent enzymes were markedly affected by the concentrations of ACH which did not affect the thiaminedependent enzyme, transketolase. In vitro studies with homogenates pre‐treated with ACH in the presence of various concentrations of glutathione showed that the latter had a protective effect against loss of transketolase activity.