Discovery and Evolution of A New Family of Nonheme Iron Aliphatic Halogenases

Regio- and stereospecific incorporation of a halogen atom to an unactivated sp³-carbon in a freestanding molecule is a challenging transformation that was absent in the inventory of enzyme-mediated reactions until recently we disclosed the first nonheme iron halogenase WelO5 that can mediate this reaction type in the context of complex indole alkaloid welwitindolinone biosynthesis (Nat Chem Biol. 2014, 10, 921-3). The initial characterization of WelO5 identified 12-epi-fischerindole U and 12-epi-hapalindole C as its native substrate. The stringent substrate requirement left an open question on whether this new type of halogenase can be evolved to become promiscuous as synthetically useful biocatalysts. In this talk, I will present biochemical evidences that WelO5-type nonheme iron halogenase is naturally evolvable. Alternation of as few as 5% of the wild type WelO5 sequences readily enhance its substrate scope.