Variants of transketolase from human erythrocytes.

Analytical isoelectric focusing and a stain for transketolase have been applied to partially purified samples of human erythrocyte hemolysates and have detected individual species of transketolase having pI values of 6.6, 7.3, 7.5, 7.8, 8.1, 8.2, 8.4 and 9.2. Six different patterns of these species were detected in 25 healthy subjects. The species of pI 7.5, 7.8 and 8.1 were common to all six patterns. Species isolated by electrofocusing could be rerun in the same system with identical pI value. The addition of thiamin diphosphate to the staining mixture darkened some but not all bands of transketolase activity. Thus human erythrocyte transketolase is heterogeneous and appears to share with human fibroblast transketolase heterogeneity for affinity of the cofactor. This heterogeneity might need recognition when thiamin nutritional sufficiency is assessed by the 'thiamin diphosphate effect' on erythrocyte transketolase.