Payer SE, Pollak H, Glueck SM, Faber K. A Rational Active-Site Redesign Converts a Decarboxylase into a C=C Hydratase: "Tethered Acetate" Supports Enantioselective Hydration of 4-Hydroxystyrenes.
ACS Catal 2018. [PMID:
29527405 PMCID:
PMC5838639 DOI:
10.1021/acscatal.7b04293]
[Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The promiscuous regio- and stereoselective hydration of 4-hydroxystyrenes catalyzed by ferulic acid decarboxylase from Enterobacter sp. (FDC_Es) depends on bicarbonate bound in the active site, which serves as a proton relay activating a water molecule for nucleophilic attack on a quinone methide electrophile. This "cofactor" is crucial for achieving improved conversions and high stereoselectivities for (S)-configured benzylic alcohol products. Similar effects were observed with simple aliphatic carboxylic acids as additives. A rational redesign of the active site by replacing the bicarbonate or acetate "cofactor" with a newly introduced side-chain carboxylate from an adjacent amino acid yielded mutants that efficiently acted as C=C hydratases. A single-point mutation of valine 46 to glutamate or aspartate improved the hydration activity by 40% and boosted the stereoselectivity 39-fold in the absence of bicarbonate or acetate.
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