Oxalyl-CoA Decarboxylase Enables Nucleophilic One-Carbon Extension of Aldehydes to Chiral α-Hydroxy Acids

Abstract

The synthesis of complex molecules from simple, renewable carbon units is the goal of a sustainable economy. Here we explored the biocatalytic potential of the thiamine-diphosphate-dependent (ThDP) oxalyl-CoA decarboxylase (OXC)/2-hydroxyacyl-CoA lyase (HACL) superfamily that naturally catalyzes the shortening of acyl-CoA thioester substrates through the release of the C₁ -unit formyl-CoA. We show that the OXC/HACL superfamily contains promiscuous members that can be reversed to perform nucleophilic C₁ -extensions of various aldehydes to yield the corresponding 2-hydroxyacyl-CoA thioesters. We improved the catalytic properties of Methylorubrum extorquens OXC by rational enzyme engineering and combined it with two newly described enzymes-a specific oxalyl-CoA synthetase and a 2-hydroxyacyl-CoA thioesterase. This enzymatic cascade enabled continuous conversion of oxalate and aromatic aldehydes into valuable (S)-α-hydroxy acids with enantiomeric excess up to 99 %.

Keywords: C1 building blocks; C−C coupling; biocatalysis; oxalyl-CoA decarboxylase; thiamine diphosphate.