Evolutionary diverse Chlamydomonas reinhardtii Old Yellow Enzymes reveal distinctive catalytic properties and potential for whole-cell biotransformations
Abstract Old Yellow Enzymes (OYEs) selectively reduce carbon‑carbon double bonds of a broad range of substrates with excellent stereoselectivity. Current challenges of their application in bio-based industrial processes are the cost-efficient regeneration of the nicotinamide co-substrate and expanding the range of industrially relevant substrates. Microalgae represent a rich and mostly untapped source for OYEs with novel catalytic properties and are promising whole-cell factories that regenerate nicotinamide by photosynthesis. By comparative phylogenetics, we identified 20 putative OYEs in eleven algal species. Three recombinant OYEs from the unicellular green alga Chlamydomonas reinhardtii (CrOYEs) reveal diverse biocatalytic properties and potential for enzyme optimization. High substrate conversion activities of living algal wild type and mutant cells linked the biocatalytic profiles to in vivo functionality and demonstrate the potential of microalgae as sources for distinctive OYE activities and for light-driven biotransformations.