Markus Wirtz

Our research focus on the regulation of cysteine synthesis by reversible protein-protein interaction of the two enzymes: serine acetyltransferase (SAT, Serat) and O-acetylserine thiol lyase (OAS-TL) that form the so called cysteine synthase complex (CSC). SAT catalyzes the formation of O-acetylserine (OAS), the carbon and nitrogen containing backbone of cysteine. OAS-TL replaces the activated acetyl group of OAS with sulfide and releases cysteine. We showed that the CSC senses the availability of OAS and sulfide and regulate SAT and OAS-TL activity to allow efficient synthesis of cysteine. Another aspect of our research is the unusual subcellular compartmentalization of SAT and OAS-TLs activities and their implications for sensing of sulfur availability in the plant cell and at the whole plant level. In this respect we also investigate the enzyme sulfite reductase (Sir), which produces sulfide and is, in contrast to SAT and OAS-TL, exclusively localized in plastids.