Complex biotransformations catalyzed by radical S-adenosylmethionine enzymes - PubMed (original) (raw)

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Complex biotransformations catalyzed by radical S-adenosylmethionine enzymes

Qi Zhang et al. J Biol Chem. 2011.

Abstract

The radical S-adenosylmethionine (AdoMet) superfamily currently comprises thousands of proteins that participate in numerous biochemical processes across all kingdoms of life. These proteins share a common mechanism to generate a powerful 5'-deoxyadenosyl radical, which initiates a highly diverse array of biotransformations. Recent studies are beginning to reveal the role of radical AdoMet proteins in the catalysis of highly complex and chemically unusual transformations, e.g. the ThiC-catalyzed complex rearrangement reaction. The unique features and intriguing chemistries of these proteins thus demonstrate the remarkable versatility and sophistication of radical enzymology.

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Figures

FIGURE 1.

FIGURE 1.

Reactions of the radical AdoMet enzymes. A, binding of AdoMet to the [4Fe-4S] cluster and the reversible carbon–sulfur bond cleavage to produce the Ado radical. The unique iron for binding of AdoMet is highlighted in yellow. B, ThiC-catalyzed formation of HMP-P from AIR. The unexpected deuterium labeling patterns are highlighted in the yellow. C, NosL/NocL-catalyzed MIA biosynthesis.

FIGURE 2.

FIGURE 2.

GTP-derived biosynthesis of Moco and deazapurine. A, role of MoaA and MoaC in Moco synthesis. B, key steps in queuosine biosynthesis. The reaction catalyzed by the radical AdoMet protein QueE is highlighted in yellow. CPH4, 6-carboxy-5,6,7,8-tetrahydropterin; CDG, 7-carboxy-7-deazaguanine.

FIGURE 3.

FIGURE 3.

Radical-mediated methylation of aromatic heterocycles. A, RNA adenine methylation catalyzed by RlmN. B, C2′ methylation of

l

-Trp, possibly involving catalysis by the radical AdoMet methyltransferase TsrT (TsrM), proceeds with the net retention of the methyl group configuration.

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