[Some properties of multiple forms of transketolase from baker's yeast]

It has been shown that transketolase A does not differ from the enzyme earlier described in the literature by a number of properties (lack of intersubunit disulfide bonds, identical number of sulfhydryl groups, two values of Km for thiamine pyrophosphate and identity of their absolute values). Transketolase C subunits are linked together by disulfide bonds; their total number in the enzyme molecule is five (transketolase C-1) or six (transketolase C-2). The Km values of transketolase C-1 for thiamine pyrophosphate are commensurate with those of transketolase A. Transketolase C-2 has only one Km value for thiamine pyrophosphate which is close to one of the two Km values for transketolase A. The maximal rate values for transketolases C-1 and C-2 with dihydroxyacetone as substrate differ by more than one order of magnitude.