This collaborative project between french and German aims at the identification and development of Transketolase (TK) variants that will tolerant specific structural modifications not (or only poorly) accessible to the wild-type enzyme. This will be achieved by a technique termed directed evolution, by which site-specifically and randomly mutated protein variants will be tested by enzymatic assays for their improved tolerance to non-natural screening probes. Among those objectives, the target defined for ketone acceptors probably is the most ambitious goal because none of the enzymes commonly studied for synthetic applications of carboligation (various aldolases, TK) is able to accept ketone electrophiles, most likely for steric hindrance. Availability of new mutant TK enzymes with novel catalytic abilities for the novel product structures as chiral building blocks will be used in the synthesis of chiral bioactive compounds and scaffolds of higher complexity.