Studies on the nature of thiamine pyrophosphate binding and dependency on divalent cations of transketolase from human erythrocytes.

1. The binding kinetics for [35S]thiamine pyrophosphate to transketolase and the dependency of transketolase on divalent cations for activity were investigated. 2. With Scatchard analysis, dissociation constant (Kd) and n value were calculated to be 0.2 x 10(-6) M and 0.66 respectively. 3. The activity of the reconstituted enzyme increased in the order of Co2+ less than Mn2+ less than Ca2+ less than Mg2+. The native transketolase contained Mg2+ in its molecular structure.