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Iron and 2-Oxoglutarate-Dependent Isonitrile-Forming Enzymes

Tzu-Yu Chen

Tzu-Yu Chen

Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695 USA

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Yisong Guo

Yisong Guo

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, 15213 USA

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Wei-chen Chang

Wei-chen Chang

Department of Chemistry, North Carolina State University, Raleigh, North Carolina, 27695 USA

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First published: 30 March 2023

Abstract

The isonitrile moiety, composed of an NC connection, is a commonly used functional group in chemical synthesis due to its highly reactive nature toward nucleophile, electrophile, and radical. Isonitrile-containing natural products have shown diverse biological properties including virulence, antimicrobial activities, and metal acquisition. Despite its abundance in natural products, how isonitrile is introduced remains understudied. Recently, N -glycinyl moiety has been identified as a biosynthon for isonitrile wherein several nonheme iron and 2-oxoglutarate-dependent (Fe/2OG) enzymes have been identified to enable this reaction. Distinct from canonical oxygenation or halogenation catalyzed by Fe/2OG enzymes, installation of the isonitrile group from a glycinyl moiety is a four-electron oxidation of the substrate and involves decarboxylation-assisted desaturation, thus representing an uncommon reaction type. To elucidate plausible reaction mechanism, several Fe/2OG-dependent enzymes involved in isonitrile-containing peptides and polyketides were characterized. Combining mechanistic probes design, protein X-ray crystallography, biochemical and biophysical characterizations, and mutagenesis, a plausible reaction pathway was established. Formation of isonitrile involves two sequential reactions. Following a CH bond cleavage triggered by an Fe(IV)-oxo, a carboxyaldimine species is produced in the first reaction. In the second reaction, decarboxylation-assisted desaturation of the carboxyaldimine intermediate affords the NC moiety.

3D Structure

Description unavailable

Schematic representation of ScoE from Streptomyces coeruleorubidus . The jellyroll motif is colored in orange, and the substrate 1 is colored in cyan stick format. PDB code: 6L6X. [Figure was prepared with PyMOL. 1 ].

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