Regulation transketolase

Transketolase 733,736 Translation of genetic information, 5. See also Protein synthesis definition of 5 nick 257 regulation of 536 Translocation... 

The transketolase and transaldolase reactions are reversible and so allow either the conversion of ribose 5-phosphate into glycolytic intermediates when it is not needed for other cellular reactions, or the generation of ribose 5-phosphate from glycolytic intermediates when more is required. The rate of the pentose phosphate pathway is controlled by NADP+ regulation of the first step, catalyzed by glucose 6-phosphate dehydrogenase. 

Later studies established the coenzyme role of thiamin diphosphate in transketolase in the pentose phosphate pathway. More recent studies have shown that thiamin triphosphate acts to regulate a chloride channel in nerve tissue. 

The transketolase activation test is in reality two tests one a measurement of basal activity and the other the degree to which the basal activity can be increased by exogenous thiamine pyrophosphate, and each may be influenced by different factors. There is evidence that chronic deficiency states of thiamine may down regulate synthesis of the apoen-zyme. In comparison studies against erythrocyte TPP concentrations, better correlations were obtained with basal activity rather than the activation coefficient. ... 

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