Johann Heider

Johann Heider

Prof. Dr. Johann Heider

Biology
Microbial Biochemistry
Karl-von-Frisch-Straße 8, 35032 Marburg
+49-6421 28 21527
heider@biologie.uni-marburg.de
http://www.uni-marburg.de/fb17/fachgebiete/mikrobio/heider

 

Research area

We are interested in the biochemistry of anaerobic hydrocarbon metabolism. All enzymic reactions involving initial attack at hydrocarbons in the absence of oxygen must be expected to follow some unusual biochemical principles, because these substrates are only turned over by oxygen-dependent mono- or dioxygenases aerobically. In particular, we study two new reaction principles of hydrocarbon-metabolism, namely fumarate addition and oxygen-independent hydroxylation. The first reaction is involved in anaerobic toluene degradation and catalyses the stereospecific formation of (R)-benzylsuccinate from toluene and fumarate by a novel glycyl radical enzyme, benzylsuccinate synthase. The second reaction initiates anaerobic ethylbenzene degradation and catalyses the stereospecific hydroxylation of ethylbenzene to (S)-1-phenylethanol by a new molybdenum enzyme. Moreover, we are characterizing the other enzymes involved in the respective pathways, which include a novel ketone carboxylase or enzymes of a beta-oxidation pathway. We are interested in identifying the respective reaction mechanisms as well as in utilizing these new reactions for biotechnological purposes.

 

Research project within SYNMIKRO

(R)-benzylsuccinate is the first intermediate of anaerobic toluene degradation and also has some potential as building block for biodegradable (co)polymers or for pharmaceuticals. Because its chemical synthesis is rather expensive, we try to exploit the enzymes of anaerobic toluene degradation to set up a bacterial production strain for (R)-benzylsuccinate. To achieve that, we will make use of the fully reversible pathway of beta-oxidation of benzylsuccinate to benzoyl-CoA, as catalyzed by five consecutive enzymes. This should yield to a novel synthetic metabolic pathway that makes use of the normal E. coli fermentation product succinate and condenses it with benzoyl-CoA and then is further converted to (R)-benzylsuccinate. The second substrate will be fed to the cells in the form of benzoate, which will have to be taken up and activated to the CoA thioester. Therefore, we have initially constructed a recombinant bacterial strain capable of converting exogenous benzoate to benzoyl-CoA and feeding it into the biosynthetic pathway of the plant polyketide 3,5-dihydroxybiphenyl. We actually succeeded in producing a secondary metabolite in Escherichia blattae containing the genes coding for a benzoate transporter, a benzoate-CoA ligase and the plant enzyme for biphenyl synthesis. This strain will now be the basis for establishing the reverse beta-oxidation pathway for benzylsuccinate synthesis.

Established (black arrows) and planned (green arrows) reactions for recombinant production of benzoyl-CoA-derived products. BenK: benzoate symporter, BclA: benzoate-CoA ligase, BIS: biphenyl synthase, BbsAB: benzoylsuccinyl-CoA thiolase, BbsCD: alcohol dehydrogenase, BbsH: phenylitaconyl-CoA hydratase, BbsG: benzylsuccinyl-CoA dehydrogenase, BbsEF: benzylsuccinate CoA-transferase. BenK and BclA are from Aromatoleum aromaticum, BIS from Sorbus acuparia, the Bbs gene products will from Thauera, Aromatoleum or Geobacter species.

SYNMIKRO Young Researchers Groups

Almost all scientific members of SYNMIKRO are actively involved in DFG’s Collaborative Research Centers (Sonderforschungsbereiche), Research Training Groups (Graduiertenkollegs), or other Cooperative Research projects. Alongside performing adventurous experiments, and reporting excellent science, SYNMIKRO substantially promotes potential Young Research Group Leaders by constantly keeping its doors open to welcome and support Young Researchers planning to set up an Independent Research Group.
Our Young Research Groups