SOME PROPERTIES OF MULTIPLE FORMS OF TRANSKETOLASE FROM BAKERS-YEAST

Transketolase A was shown to have the same properties as transketolases described in the literature: lack of intersubunit disulfide bonds; same 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 the values of K-m with thiamine pyrophosphate. With thiamine pyrophosphate, 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 magnitude.