23] Transketolase (sedoheptulose-7-phosphate:d-glyceraldehyde-3-phosphate dihydroxyacetonetransferase, EC 2.2.1.1) and the TPP effect in assessing thiamine adequacy

Abstract

This chapter discusses transketolase and the thiamine pyrophosphate (TPP) effect in assessing thiamine adequacy. The transketolase enzyme is of interest to the nutritionist because thiamine pyrophosphate, the functional form of vitamin B 1 , is its coenzyme. It is one of a series of enzymes in the pentose phosphate pathway, and it is widely distributed in tissues of plants, microorganisms, and animals. The chapter describes the assay for transketolase activity and the TPP effect. The assay has been employed with success in a number of species, both in the study of biological interrelationships of thiamine deficiency and in the assessment of thiamine adequacy in man. A similar semimicroassay is described in the chapter. The macroassay has been adapted for use also under automated conditions. Erythrocyte transketolase activity and the TPP effect present a functional evaluation, which is both sensitive to and specific for thiamine deficiency. It may be used to confirm clinical beriberi or other manifestations such as Wernicke's encephalopathy, to reveal a biochemical defect in marginal vitamin B 1 deficiency, or to differentiate B 1 deficiency from clinically similar diseases of other etiology.