Paper ID: 264
1 Goethe-University Frankfurt, Institute of Molecular Biosciences (Germany)
2 Goethe-University Frankfurt (Germany)
The efficiency and flux of metabolic pathways can be hampered by factors like slow diffusion rates, competing pathways or secretion of pathway intermediates. Genetic engineering of new metabolic pathways for biotechnological purposes is often influenced by the same limitations. In nature, such limitations are bypassed by compartimentalization of enzymatic reactions in organelles or multi-enzyme complexes. Various examples of interactions between enzymes catalyzing sequential reactions are known, by which the transfer of reaction intermediates from one active site to the other is accelerated. Direct channeling is achieved within stable multi-enzyme assemblies or by a precise alignment of active centers in a single polypeptide chain. On the other hand, there are examples of enzymes that are co-localized by scaffold proteins, membranes, or cytoskeleton. In such enzyme agglomerates the fast hand-over of intermediates is facilitated by increased local concentrations of reaction partners.
We are developing new concepts for metabolic pathway engineering to assemble enzymes and transporters in protein supercomplexes and to relocate metabolic pathways into synthetic organelles. As an example we will show that by constructing an artificial complex between a sugar transporter and a xylose isomerase in baker’s yeast the consumption of xylose was accelerated due to the direct feeding of the enzyme through the transporter. Concomitantly, the production of xylitol as an undesired side-product could be significantly diminished and the production of ethanol could be increased (Thomik et al., Nat Chem Biol, in press).
On the other hand, genetic engineering of existing multi-enzyme complexes is often difficult to achieve due to missing information about the structures, reaction mechanisms and interactions between the individual domains. Nevertheless, we will show how we have recently successfully re-engineered the fatty acid synthase complex of yeast for the production of valuable short- and medium-chain fatty acids, like C8-octanoic acid (Gajewski et al. 2017, Nat Commun 8:14650).