Hydroxylation and Dihydroxylation

Holland, Herbert L.

doi:10.1002/9783527620999.ch10h

Cited by 2 publications

(1 citation statement)

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“…Moreover, CrP was found to brominate phe- nol, resulting in the formation of 2-bromo-and 4-bromophenol, and remarkably, it was capable of selectively hydroxylating naphthalene. The latter reaction is of particular interest since the incorporation of oxygen into aromatic substrates is necessary to activate inert organic substances and is thought to be a specific feature of intracellular mono-and dioxygenases (2,19,39). The results of our study give reason to assume that enzymes acting as extracellular aromatic peroxygenases are widespread among agaric basidiomycetes.…”

Section: Discussionmentioning

confidence: 72%

The Coprophilous Mushroom Coprinus radians Secretes a Haloperoxidase That Catalyzes Aromatic Peroxygenation

Anh

Ullrich

Benndorf

et al. 2007

Appl Environ Microbiol

107

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Coprophilous and litter-decomposing species (26 strains) of the genus Coprinus were screened for peroxidase activities by using selective agar plate tests and complex media based on soybean meal. Two species, Coprinus radians and C. verticillatus, were found to produce peroxidases, which oxidized aryl alcohols to the corresponding aldehydes at pH 7 (a reaction that is typical for heme-thiolate haloperoxidases). The peroxidase of Coprinus radians was purified to homogeneity and characterized. Three fractions of the enzyme, CrP I, CrP II, and CrP III, with molecular masses of 43 to 45 kDa as well as isoelectric points between 3.8 and 4.2, were identified after purification by anion-exchange and size exclusion chromatography. The optimum pH of the major fraction (CrP II) for the oxidation of aryl alcohols was around 7, and an H 2 O 2 concentration of 0.7 mM was most suitable regarding enzyme activity and stability. The apparent K m values for ABTS [2,2-azinobis(3-ethylbenzthiazolinesulfonic acid)], 2,6-dimethoxyphenol, benzyl alcohol, veratryl alcohol, and H 2 O 2 were 49, 342, 635, 88, and 1,201 M, respectively. The N terminus of CrP II showed 29% and 19% sequence identity to Agrocybe aegerita peroxidase (AaP) and chloroperoxidase, respectively. The UV-visible spectrum of CrP II was highly similar to that of resting-state cytochrome P450 enzymes, with the Soret band at 422 nm and additional maxima at 359, 542, and 571 nm. The reduced carbon monoxide complex showed an absorption maximum at 446 nm, which is characteristic of heme-thiolate proteins. CrP brominated phenol to 2-and 4-bromophenols and selectively hydroxylated naphthalene to 1-naphthol. Hence, after AaP, CrP is the second extracellular haloperoxidase-peroxygenase described so far. The ability to extracellularly hydroxylate aromatic compounds seems to be the key catalytic property of CrP and may be of general significance for the biotransformation of poorly available aromatic substances, such as lignin, humus, and organopollutants in soil litter and dung environments. Furthermore, aromatic peroxygenation is a promising target of biotechnological studies.

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Section: Discussionmentioning

confidence: 72%

The Coprophilous Mushroom Coprinus radians Secretes a Haloperoxidase That Catalyzes Aromatic Peroxygenation

Anh

Ullrich

Benndorf

et al. 2007

Appl Environ Microbiol

107

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Enzymatic hydroxylation of aromatic compounds

Ullrich

Hofrichter

2007

Cell. Mol. Life Sci.

299

182

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Selective hydroxylation of aromatic compounds is among the most challenging chemical reactions in synthetic chemistry and has gained steadily increasing attention during recent years, particularly because of the use of hydroxylated aromatics as precursors for pharmaceuticals. Biocatalytic oxygen transfer by isolated enzymes or whole microbial cells is an elegant and efficient way to achieve selective hydroxylation. This review gives an overview of the different enzymes and mechanisms used to introduce oxygen atoms into aromatic molecules using either dioxygen (O(2)) or hydrogen peroxide (H(2)O(2)) as oxygen donors or indirect pathways via free radical intermediates. In this context, the article deals with Rieske-type and alpha-keto acid-dependent dioxygenases, as well as different non-heme monooxygenases (di-iron, pterin, and flavin enzymes), tyrosinase, laccase, and hydroxyl radical generating systems. The main emphasis is on the heme-containing enzymes, cytochrome P450 monooxygenases and peroxidases, including novel extracellular heme-thiolate haloperoxidases (peroxygenases), which are functional hybrids of both types of heme-biocatalysts.

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Hydroxylation and Dihydroxylation

Cited by 2 publications

References 301 publications

The Coprophilous Mushroom Coprinus radians Secretes a Haloperoxidase That Catalyzes Aromatic Peroxygenation

The Coprophilous Mushroom Coprinus radians Secretes a Haloperoxidase That Catalyzes Aromatic Peroxygenation

Enzymatic hydroxylation of aromatic compounds

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