Substrate Specificity and Regioselectivity of Tryptophan 7-Halogenase from Pseudomonas fluorescens BL915

Hölzer, Manuela; Burd, Wassily; Reißig, Hans‐Ulrich; Pée, Karl‐Heinz van

doi:10.1002/1615-4169(200108)343:6/7<591::aid-adsc591>3.3.co;2-5

Cited by 28 publications

(50 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…They were discovered when the biosynthesis of the antifungal agent pyrrolnitrin was investigated (34). One of the enzyme involved (PnrA) is a tryptophan halogenase able to halogenate in a site-specific manner L-tryptophan to obtain 7-chlorotryptophan, and in this case the exact positioning of the biosynthetic intermediate at the active site of the enzyme seemed to be of major importance (35). Further investigations also demonstrated that FAD and the chloride residue were bound at the same site (36).…”

Section: Discussionmentioning

confidence: 99%

Identification of a Halogenase Involved in the Biosynthesis of Ochratoxin A in Aspergillus carbonarius

Ferrara

Perrone

Gambacorta

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

Aspergillus carbonarius is the main responsible fungus of ochratoxin A (OTA) contamination of grapes and derived products. To date, the biosynthetic mechanism of this mycotoxin has been partially elucidated. Availability of genome sequence of A. carbonarius has allowed the identification of a putative gene cluster involved in OTA biosynthesis. This region hosts the previously characterized AcOTAnrps and AcOTApks genes encoding two key enzymes of the biosynthetic pathway. At about 4,400 nucleotides downstream of these loci, a gene encoding a putative flavin dependent-halogenase came out from the annotation data. Its proximity to OTA biosynthetic genes and its sequence analysis have suggested a role in the biosynthesis of OTA, directed to the introduction of the chlorine atom in the C-5 position of the final molecular structure of this mycotoxin. The deduced protein sequence of the halogenase gene, we designated AcOTAhal, shows a high similarity to a halogenase that is located in the OTA cluster of A. niger. The deletion of the halogenase gene completely eliminated the production of ochratoxin A in A. carbonarius and determined a significant increase of ochratoxin B, as confirmed by mass spectrometry analysis. Moreover, its expression profile was similar to the two biosynthetic genes previously identified, AcOTApks and AcOTAnrps, indicating a strong correlation of the AcOTAhal gene with the kinetics of OTA accumulation in A. carbonarius. Therefore, experimental evidence confirmed that the chlorination step which converts OTB in OTA represents the final stage of the biosynthetic pathway, supporting our earlier hypothesis on the order of enzymatic steps of OTA biosynthesis in A. carbonarius. IMPORTANCEOchratoxin A is a potent mycotoxin classified as a possible carcinogen for humans, and Aspergillus carbonarius is the main agent responsible for OTA accumulation in grapes. We demonstrate here that a flavin-halogenase is implicated in the biosynthesis of OTA in A. carbonarius. The encoding gene, AcOTAhal, is contiguous to biosynthetic genes that we have already described (nrps and pks), resulting as part of the biosynthetic cluster. The encoded protein is responsible of the introduction of chlorine atom in the final molecular structure and acts at the last step in the pathway. This study can be considered a continuation of an earlier study wherein we started to clarify the molecular basis of OTA biosynthesis in A. carbonarius, which has not been completely elucidated until now. This research represents an important step forward to a better understanding of the production mechanism, which will contribute to the development of improved control strategies to reduce the risk of OTA contamination in food products.

show abstract

Section: Discussionmentioning

confidence: 99%

Identification of a Halogenase Involved in the Biosynthesis of Ochratoxin A in Aspergillus carbonarius

Ferrara

Perrone

Gambacorta

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…Noteworthy here is the observation that tryptophan halogenases also demonstrate broad substrate tolerance, albeit with reduced catalytic efficiencies, towards a wide swathe of electron rich substrates. 87–89 Advances in the identification of the physiological substrate for a fungal FDH was provided by the recent study examining the biosynthesis of chaetoviridin A ( 20 ) from Chaetomiun globosum via the caz biosynthetic gene cluster. 90 The postulated small molecule substrate for the FDH CazI accumulates in the culture extracts when the cazI gene is deleted, and the chlorination of this accumulated small molecule was experimentally demonstrated by the FDH CazI.…”

Section: Flavin-dependent Halogenasesmentioning

confidence: 99%

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

“…Thus far, most of this work has been focussed on the tryptophan halogenases and has revealed a number of enzymes capable of halogenating tryptophan derivatives, 218 non-natural indolic substrates, 150,155,[219][220][221] in addition to benzamides and benzoic acids 150,155 as well as napthols and napthyl amines (Figure 19). 220,221 In a number of cases, halogenation occurs with good regioselectivity.…”

Section: Substrate Scope Of Fl-halsmentioning

confidence: 99%

“…220,221 The formation of dichlorinated products and regioisomers has also been observed from the halogenation of tryptophan derivatives bearing electron-donating substituents with RebH (61 to 63), and in the halogenation of 3-(2'-aminophenyl)pyrrole (64) with the highly activated substrate 64, seven halogenated products were formed (including regioisomers and di-chlorinated products) due to the electron-rich nature of both the pyrrole and aniline moieties. 219 Most of the tryptophan halogenases have also been shown to chlorinate both L-and Dtryptophan, with preference for the natural L-enantiomer. [219][220][221] In an attempt to broaden substrate scope of the enzymatic halogenation, the tryptophan-5-and tryptophan-6-halogenases PyrH and SttH have also been studied.…”

Section: Substrate Scope Of Fl-halsmentioning

confidence: 99%

“…219 Most of the tryptophan halogenases have also been shown to chlorinate both L-and Dtryptophan, with preference for the natural L-enantiomer. [219][220][221] In an attempt to broaden substrate scope of the enzymatic halogenation, the tryptophan-5-and tryptophan-6-halogenases PyrH and SttH have also been studied. With a number of 2-amino benzamides and benzoic acids (67 to 72), PyrH and SttH were found to solely chlorinate para to the -NH 2 , whilst PrnA afforded mixtures of both ortho-and para-chlorinated products in most cases.…”

Section: Substrate Scope Of Fl-halsmentioning

confidence: 99%

See 1 more Smart Citation

Development of Halogenase Enzymes for Use in Synthesis

Latham

Brandenburger

Shepherd³

et al. 2017

Chem. Rev.

286

244

View full text Add to dashboard Cite

Nature has evolved halogenase enzymes to regioselectively halogenate a diverse range of biosynthetic precursors, with the halogens introduced often having a profound effect on the biological activity of the resulting natural products. Synthetic endeavours to create non-natural bioactive small molecules for pharmaceutical and agrochemical applications have also arrived at a similar conclusion -halogens can dramatically improve the properties of organic molecules for selective modulation of biological targets in vivo. Consequently a high proportion of pharmaceuticals and agrochemicals on the market today possess halogens. Halogenated organic compounds are also common intermediates in synthesis and are particularly valuable in metal catalyzed cross-coupling reactions.Despite the potential utility of organohalogens, traditional non-enzymatic halogenation chemistry utilizes deleterious reagents and often lacks regiocontrol. Reliable, facile and cleaner methods for the regioselective halogenation of organic compounds are therefore essential in the development of economical and environmentally-friendly industrial processes. A potential avenue towards such methods is the use of halogenase enzymes, responsible for the biosynthesis of halogenated natural products, as biocatalysts. This review will discuss the advances towards this goal thus far, in addition to untapped potential sources of such biocatalysts and how further development of the enzymes may be focused in order to achieve the goal of industrial scale biohalogenation.

show abstract

Substrate Specificity and Regioselectivity of Tryptophan 7-Halogenase from Pseudomonas fluorescens BL915

Cited by 28 publications

References 0 publications

Identification of a Halogenase Involved in the Biosynthesis of Ochratoxin A in Aspergillus carbonarius

Identification of a Halogenase Involved in the Biosynthesis of Ochratoxin A in Aspergillus carbonarius

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse

Development of Halogenase Enzymes for Use in Synthesis

Contact Info

Product

Resources

About