Evidence for the Presence of Thiamin Diphosphate Kinase in Human Erythrocytes

A thiamin diphosphate (TDP) kinase (EC 2.7.4.15), which catalyzes the synthesis of thiamin triphosphate (TTP) from TDP, was found in erythrocytes after the freezing and thawing of human blood. The enzyme was biochemically distinct from the kinase previously reported. The enzyme activity was accelerated by Fe2+ and Fe3+ and inhibited by trichloroacetic acid, SH-blocking reagents and EDTA. It was suggested that the enzyme would have a sulfhydryl group at the active site, and requires certain cofactors for its activity.