SOME PROPERTIES OF MULTIPLE FORMS OF TRANSKETOLASE FROM BAKERS-YEAST

Transketolase A was shown to have the same properties as transketolase s described in the literature: lack of intersubunit disulfide bonds; s ame number of sulfhydryl groups; two distinct K-m values with thiamine pyrophosphate with no differences in their absolute values among the enzymes. The subunits of transketolase C are linked by disulfide bonds . Their total number is five (transketolase C-l) or six (transketolase C-2). There are no differences between transketolases C-1 and A in th e values of K-m with thiamine pyrophosphate. With thiamine pyrophospha te, transketolase C-2 exhibits only one K-m; it is close to one of the two K-m values determined for transketolase A. When dihydroxyacetone is used as substrate, the difference between transketolases C-l and C- 2 in the values of the maximal reaction rate exceeds one order of magn itude.