Mechanisms of Enzymatic Vinyl Isonitrile Formation and Reprogramming of Isonitrilases and Iron/2-Oxoglutarate Desaturases

Project Summary/Abstract
Isonitrilase is involved in constructing a triple bond from a primary amine and a carbonyl moiety of carbohydrate
phosphate. Non-heme iron and 2-(oxo)glutarate-dependent (Fe/2OG) enzymes catalyze a bewildering array of
transformations, which include halogenations, cyclizations, dehydrogenations, endoperoxidation and
stereoinversion of aliphatic carbon centers. In more than 40 isolated vinyl isonitrile containing natural products,
a universal approach involving a consecutive two-step enzymatic transformation by an isonitrilase and an
Fe/2OG dependent alkene forming enzyme is proposed to install these functional groups. However, the
mechanistic understating of these transformations remains to be elucidated. A chemical and biosynthetic
understanding of these reaction mechanisms could enable reprograming of isonitrilase and Fe/2OG enzymes
as biocatalysts for producing new compounds with improved bioactivity. Having recently made progress toward
Fe/2OG enzyme catalyzed epoxidation and desaturation, and isonitrilase activity reconstitution in vitro, we
propose to study the isonitrile and decarboxylation-assisted alkene formation reactions on the pathway to
rhabduscin and paerucumarin biosyntheses. We will use an integrated approach to provide molecular
understanding of the enzyme mechanisms and, in select cases, evaluate the substrate flexibility and reprogram
the related enzymes by directed evolution.