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 erythro cytes after the freezing and thawing of human blood. The enzyme was bi ochemically distinct from the kinase previously reported. The enzyme a ctivity was accelerated by Fe2+ and Fe3+ and inhibited by trichloroace tic acid, SH-blocking reagents and EDTA. It was suggested that the enz yme would have a sulfhydryl group at the active site, and requires cer tain cofactors for its activity.