Ketones and imines as substrates of ThDP-dependent enzymes

• Applicant: Professor Dr. Michael Müller
• Subject Area: Biological and Biomimetic Chemistry
• Term: from 2010 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 128900243

YerE plays a unique role amongst thiamine diphosphate {ThDP)-dependent enzymes accepting not only two aldehydes as substrates for benzoin condensation. Moreover, it is the first enzyme known so far, that catalyzes an intermolecular enantioselective crossed carboligation between aldehydes and ketones giving rise to chiral tertiary alcohohls. Thus, the use of the catalyst YerE permits the access to a further important building block with ThDP-dependent enzymes, besides the already established synthesis of chiral 2-hydroxy ketones with benzaldehyde lyase (BAL) and diverse pyruvate decarboxylases (PDCs). The aim of this project is to acquire a profound knowledge of this unusual ThDP-dependent enzyme and its catalyzed reaction. A detailed analysis of the biochemistry and structure of YerE will offer new information concerning the catalytic mechanism of the protein and could reveal the differences to other well-known ThDP-dependent enzymes like BAL or PDC, which have been intensively studied but do not catalyze the conversion of ketones. In contrast to the ThDP-dependent enzyme cyclohexane-1,2-dione hydrolase (CDH), which like YerE accepts 1,2-diketones as substrates, YerE catalyzes a completely different reaction that does not cleave the C-C bond in a cyclic diketone. In this respect, the parallel examination of the enzymes YerE {this project) and CDH (project 8) is of great interest for the Research Unit to identify the parameters that are determining the specific reactions. In the long run, profound insight in mechanism, function and structure of ThDP-dependent enzymes should enable the design of biocatalysts with desired properties on the one hand and support prediction of the activity of an unknown enzyme on the other hand. tn addition, this project not only investigates an exceptional ThDP-dependent enzyme, YerE, the catalyzed crossed aldehyde-ketone carboligation offers a new way for the catalytic asymmetric formation of chiral tertiary alcohols. Testing the substrate range on the donor, as well as on the acceptor side will show the whole palette of accessible compounds. As the thus obtained tertiary alcohols possess functionalities that are easily transformable to other ones, e.g. diols or amino derivatives, these substances are highly relevant candidates for various applications in chemistry and biology.

• DFG Programme: Research Units
• Subproject of: FOR 1296: Diversity of Asymmetric Thiamine Catalysis