Unusual flavoenzyme catalysis in marine bacteria

Teufel, Robin; Agarwal, Vinayak; Moore, Bradley S.

doi:10.1016/j.cbpa.2016.01.001

Cited by 63 publications

(51 citation statements)

References 53 publications

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“…As such, the currently proposed halide binding site for flavin-dependent halogenases is itself debatable (29), thus underscoring the challenges associated with teasing apart the role of the enzymatic halogenase catalyst in each of the requisite mechanistic steps. Discovery and characterization of additional flavin-dependent halogenases promises to provide opportunities to answer these mechanistic questions, ultimately leading to engineerable toolkits to tailor the biosynthesis of halogenated natural products (30).…”

Section: Discussionmentioning

confidence: 99%

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

Gamal

Agarwal

Diethelm

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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118

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Halogenated pyrroles (halopyrroles) are common chemical moieties found in bioactive bacterial natural products. The halopyrrole moieties of mono-and dihalopyrrole-containing compounds arise from a conserved mechanism in which a proline-derived pyrrolyl group bound to a carrier protein is first halogenated and then elaborated by peptidic or polyketide extensions. This paradigm is broken during the marine pseudoalteromonad bacterial biosynthesis of the coral larval settlement cue tetrabromopyrrole (1), which arises from the substitution of the proline-derived carboxylate by a bromine atom. To understand the molecular basis for decarboxylative bromination in the biosynthesis of 1, we sequenced two Pseudoalteromonas genomes and identified a conserved four-gene locus encoding the enzymes involved in its complete biosynthesis. Through total in vitro reconstitution of the biosynthesis of 1 using purified enzymes and biochemical interrogation of individual biochemical steps, we show that all four bromine atoms in 1 are installed by the action of a single flavin-dependent halogenase: Bmp2. Tetrabromination of the pyrrole induces a thioesterase-mediated offloading reaction from the carrier protein and activates the biosynthetic intermediate for decarboxylation. Insights into the tetrabrominating activity of Bmp2 were obtained from the high-resolution crystal structure of the halogenase contrasted against structurally homologous halogenase Mpy16 that forms only a dihalogenated pyrrole in marinopyrrole biosynthesis. Structure-guided mutagenesis of the proposed substrate-binding pocket of Bmp2 led to a reduction in the degree of halogenation catalyzed. Our study provides a biogenetic basis for the biosynthesis of 1 and sets a firm foundation for querying the biosynthetic potential for the production of 1 in marine (meta)genomes.natural products | biosynthesis | halogenation | enzymology

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Section: Discussionmentioning

confidence: 99%

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

Gamal

Agarwal

Diethelm

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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118

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“…While a halide binding site has been identified at the re face of the cofactor isoalloxazine ring, whether this a productive site for halide binding has been debated in the literature. 24,40 …”

Section: Flavin-dependent Halogenasesmentioning

confidence: 99%

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse

et al. 2017

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Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature’s halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.

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“…So far S. davawensis has recruited and adjusted rosB and rosA to generate apotent antibiotic and eventually (in the time course of further evolution) these genes may be co-transcribed as it is the case for many other genes involved in secondary metabolism. [17] a) Anion hole of RosB in which species with (partially) negative charges can be stabilized.…”

Section: Communicationsmentioning

confidence: 99%

The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin‐like Enzymes

et al. 2016

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8-demethyl-8-aminoriboflavin-5'-phosphate (AFP) synthase (RosB) catalyzes the key reaction of roseoflavin biosynthesis by forming AFP from riboflavin-5'-phosphate (RP) and glutamate via the intermediates 8-demethyl-8-formylriboflavin-5'-phosphate (OHC-RP) and 8-demethyl-8-carboxylriboflavin-5'-phosphate (HO C-RP). To understand this reaction in which a methyl substituent of an aromatic ring is replaced by an amine we structurally characterized RosB in complex with OHC-RP (2.0 Å) and AFP (1.7 Å). RosB is composed of four flavodoxin-like subunits which have been upgraded with specific extensions and a unique C-terminal arm. It appears that RosB has evolved from an electron- or hydride-transferring flavoprotein to a sophisticated multi-step enzyme which uses RP as a substrate (and not as a cofactor). Structure-based active site analysis was complemented by mutational and isotope-based mass-spectrometric data to propose an enzymatic mechanism on an atomic basis.

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Unusual flavoenzyme catalysis in marine bacteria

Cited by 63 publications

References 53 publications

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse

The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin‐like Enzymes

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