Asymmetric Proton Transfer Catalysis by Stereocomplementary Old Yellow Enzymes for C═C Bond Isomerization Reaction

Native and promiscuous catalytic activities of flavin-dependent Old Yellow Enzymes (OYEs) reported to date are initiated by the reduced flavin upon electron transfer. As a rare exception, isomerization nonactivated C═C bond was shown be hydride-independent with two nonstereoselective yeast OYEs. Here, we report asymmetric prochiral model substrate, γ-methyl β,γ-butenolide, corresponding (R)- (S)-enantiomers α,β-butenolide in up >99% ee stereocomplementary OYEs algal fungal origin, respectively, which operate proton Mechanistic studies based on newly solved crystal structures, along soaking experiments site-directed mutagenesis, support crucial role partially nonconserved tyrosine residues for activity stereoselectivity both (S)-isomerases. This study offers unique view potential flavoproteins nonredox catalysis provides hints scouting olefin isomerases likely stereodivergent classes