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Lookup NU author(s): Emeritus Professor Bernard Golding
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4-Hydroxyphenylacetate decarboxylase (4Hpad) is the prototype of a new class of Fe-S cluster-dependent glycyl radical enzymes (Fe-S GREs) acting on aromatic compounds. The two-enzyme component system comprises a decarboxylase responsible for substrate conversion and a dedicated activating enzyme (4Hpad-AE). The decarboxylase uses a glycyl/thiyl radical dyad to convert 4-hydroxyphenylacetate into p-cresol (4-methylphenol) by a biologically unprecedented Kolbe-type decarboxylation. In addition to the radical dyad prosthetic group, the decarboxylase unit contains two [4Fe-4S] clusters coordinated by an extra small subunit of unknown function. 4Hpad-AE reductively cleaves S-adenosylmethionine (SAM or AdoMet) at a site-differentiated [4Fe-4S](2+/+) cluster (RS cluster) generating a transient 5'-deoxyadenosyl radical that produces a stable glycyl radical in the decarboxylase by the abstraction of a hydrogen atom. 4Hpad-AE binds up to two auxiliary [4Fe-4S] clusters coordinated by a ferredoxin-like insert that is C-terminal to the RS cluster-binding motif. The ferredoxin-like domain with its two auxiliary clusters is not vital for SAM-dependent glycyl radical formation in the decarboxylase, but facilitates a longer lifetime for the radical. This review describes the 4Hpad and cognate AE families and focuses on the recent advances and open questions concerning the structure, function and mechanism of this novel Fe-S-dependent class of GREs. (C) 2016 S. Karger AG, Basel
Author(s): Selvaraj B, Buckel W, Golding BT, Ullmann GM, Martins BM
Publication type: Review
Publication status: Published
Journal: Journal of Molecular Microbiology and Biotechnology
Year: 2016
Volume: 26
Issue: 1-3
Pages: 76-91
Print publication date: 01/03/2016
Online publication date: 10/03/2016
Acceptance date: 01/01/1900
ISSN (print): 1464-1801
ISSN (electronic): 1660-2412
Publisher: KARGER
URL: http://dx.doi.org/10.1159/000440882
DOI: 10.1159/000440882
