Below is a model for the assembly of transketolase, a ThDP-requiring enzyme (in the model, TPP is used for thiamine diphosphate instead of ThDP based on older nomenclature). In humans, step c or dimerization usually occurs readily due to an assembly factor resulting in the posttranslational modification of the monomeric transketolase. The required factor(s) was found to be defective in a Wernicke-Korsakoff patient whose cells in culture show an enhanced sensitivity to thiamine deficiency. We believe that a defect in this factor is one mechanism that results in an individual being hypersensitive to thiamine deficiency and in the formation of brain damage. See Alcohol Clin Exp Res 21:576-580 (1997) for details.