Enzymes of the microbial catabolism of the thioether 3,3´-thiodipropionic acid

• Applicant: Professor Dr. Alexander Steinbüchel
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms ; Microbial Ecology and Applied Microbiology
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 255339739

The proposed project investigates the rare microbial degradation of the organic sulfur compound and thioether 3,3´-thiodipropionic acid (TDP) as sole carbon source. The previously isolated beta-proteobacterium Variovorax paradoxus strain TBEA6 is the most favourable candidate to elucidate TDP catabolism of TDP; it serves as a model organism and is employed in this project. Most genes and their translational products, which are putatively involved in the catabolic pathway of TDP, were previously identified by our laboratory. A detailed biochemical characterization of the key enzyme of this pathway, the 3-mercaptopropionate dioxygenase (Mdo), was already done. Mdo catalyzes the second step of the proposed pathway, the oxidation of the sulfhydryl group of 3-mercaptopropionate (3MP) into a sulfino group, thereby forming 3-sulfinopropionate. However, the important initial steps, i. e. the transport of TDP into the cell and its subsequent cleavage of TDP into 3-hydroxypropionic acid and 3MP, are only suppositions, yet. The assumed transport system belongs to the TTT (Tripartite Tricarboxylate Transport) family. The enzyme putatively responsible for the cleavage of TDP is a novel FAD-dependent oxidoreductase. These reactions are in the major focus of this project. In addition, the proposed activation of the intermediate 3-sulfinopropionic acid into 3-sulfinopropionyl-CoA, which is catalyzed by a CoA ligase, and the subsequent desulfination reaction performed by an acyl-CoA dehydrogenase-like desulfinase will be investigated in detail. Thus, during this project in vitro and in vivo enzyme assays will be developed and optimized (i). Moreover, the whole-genome DNA of V. paradoxus strain TBEA6 was sequenced by the Göttingen Genomics Laboratory (G2L), and will be processed and annotated (ii). Subsequently, proteome studies during growth on TDP and alternative carbon sources will be accomplished (iii). The findings will be used for the enhanced biotechnological production of polythioesters based on the nontoxic precursor TDP.

• DFG Programme: Research Grants