Activation of the hydroxylase of sMMO from Methylococcus capsulatus (Bath) by hydrogen peroxide

Jiang, Yan; Wilkins, Patricia C.; Dalton, Howard

doi:10.1016/0167-4838(93)90285-y

Cited by 55 publications

(63 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Using as a model the diiron peroxo intermediate suggested in a recent paper [23], these possibilities are illustrated below. Our peroxide shunt experiments, in which the iron-peroxo species is likely to be formed directly, are also indicative of 0 atom Ph Ph Peroxo Fenyl addition [24]. In the H,O,-driven catalysis of the oxidation of trans-2-butene there is a dramatic shift in product distribution compared to that in the conventional reaction catalysed by native soluble methane monooxygenase.…”

Section: Styrenementioning

confidence: 63%

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Wilkins

Dalton

Samuel

et al. 1994

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

The data from the deuterium isotope experiments in this study show that the primary kinetic isotope effect for methane oxidation catalysed by soluble methane monooxygenase from Methylococcus capsulatus (Bath) is very small, <2. In contrast, the primary kinetic isotope effect for -CH, group oxidation in toluene is large, > 7. A mechanistic pathway in which a substrate radical is formed from hydrogen atom abstraction by a ferry1 species is believed to operate for CH,, the toluene -CH, group and similar alkanes. Direct oxygen atom addition, rather than H atom abstraction, is indicated for aromatic ring oxidations in benzene and toluene and for styrene oxide formation from styrene. Thus, more than one mechanistic pathway appears to operate in soluble methanemonooxygenase-catalysed reactions and, in some cases, the pathway chosen may be dictated by the substrate.In the soluble methane-monooxygenase-catalysed oxidation of toluene the rates of: (a) substrate dissociation from the enzyme-substrate complex, (b) product formation and (c) product release (benzyl alcohol and p-cresol) from the enzyme-product complex are comparable in magnitude. Therefore all three of these steps are partially rate-determining in the soluble methane monooxygenase catalytic cycle for toluene oxidation.The active site of the enzyme soluble methane monooxygenase [l] is just one example of the bridged diiron motif now known to occur in a number of non-heme iron proteins of vastly different functions [2]. In the case of soluble methane monooxygenase the function of the diiron site is to activate 0, so that one of the oxygen atoms is inserted into a methane C-H bond to form methanol. The other oxygen atom ends up in the second product, water. The enzyme consists of three components : the hydroxylase, the reductase and a regulatory protein, component B. The p-OH bridged diiron site [3, 41 resides in the hydroxylase and it is the fully reduced, Fe(II)Fe(II), form which is catalytically active [5]. 25).National Institutes of Health.high-valent iron-oxo intermediate, forming a substrate radical which then rapidly reacts with iron-bound OH to produce the product [9-111. This mechanism is, in many respects, similar to that proposed for cytochrome P-450 (121. It has been shown that P-450-catalysed hydroxylation of toluene produces benzyl alcohol plus o-, m-and p-cresols with benzyl alcohol as the major product [13 1. With fully deuterated toluene the product ratio was reversed and the cresols dominated. We had earlier observed that catalysis of toluene oxidation by soluble methane monooxygenase produced benzyl alcohol and only p-cresol (not ortho and metu) [8,9, 141. Recently Rataj et al. [15] reported that benzyl alcohol alone and no p-cresol was produced in this oxidation of toluene using soluble methane monooxygenase from Methylosinus trichosporium and crude extract from Methylococcus cupsulutus (Bath). They were also unable to detect any styrene oxide when styrene was used as substrate, a product we had observed previously with the M. cupsulutus ...

show abstract

Section: Styrenementioning

confidence: 63%

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Wilkins

Dalton

Samuel

et al. 1994

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…The native hydroxylase preparations in this study contained 1.8-2.0 mol Fe/mol protein and apohydroxylase preparations contained 0.05 -0.2 mol Fe/mol apoprotein. Native [28] and H,O,-driven [29] enzyme activity assays were performed as described previously.…”

Section: Methodsmentioning

confidence: 99%

Abduction of iron(III) from the soluble methane monooxygenase hydroxylase and reconstitution of the binuclear site with iron and manganese

Atta

Fontecave

Wilkins

et al. 1993

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

The apo-form of the soluble methane monooxygenase hydroxylase from Methylococcus capsulatus (Bath) was prepared via chelation of iron(II1) with 3,4-dihydroxybenzaldehyde. The apohydroxylase was reconstituted by the anaerobic addition of Fe(I1) followed by air oxidation. The enzyme thus prepared regained 85-90% of its original catalytic activity. The incorporation of two manganese(I1) ions/mol of apohydroxylase was monitored by EPR spectroscopy. The Mn(I1) ions occupy the native diiron active site and remain in the +2 oxidation state. The EPR data suggest strong coupling between the two Mn(I1) ions and retention of the p-hydroxo (alkoxo) bridge. The results of this study indicate that the M. capsulutus (Bath) hydroxylase contains a single diiron site.Methane monooxygenase (MMO) efficiently catalyses the conversion of methane to methanol at ambient temperature and pressure. There are two forms of the enzyme, soluble (sMMO) or membrane-bound particulate (pMMO), the occurrence of which depends on the Cu2+ : biomass ratio under which the cells are grown [l]. Soluble methane monooxygenase has been the more studied and is a three-component enzyme system as isolated from several different organisms [2-71. Electrons from NADH are passed through the FAD and Fe2S, centers of the reductase to the hydroxylase [2, 81. The third component, protein B, contains no metal ions nor cofactors and is believed to have a regulatory function [9-111.The hydroxylase has been shown to be the component within which oxidation of methane and a variety of other substrates occurs 141. The active site is a p-hydroxo-bridged or -alkoxo-bridged diiron cluster [12-141 similar to those found in other nonheme iron-oxo proteins like the R2 subunit of ribonucleotide reductase, hemerythrin, purple acid phosphatases and rubrcrythrin [ 15 -191. The diiron centers perform very different functions in each of these metalloproteins. In R2 a stable tyrosyl radical is generated, in hemerythrin oxygen is bound reversibly, purple acid phosphatases catalyse the hydrolysis of phosphate esters and sMMO catalyses the oxidation of many alkane, alkene, heterocyclic and aromatic compounds. The X-ray crystal structures of the R2 subunit and hemerythrin have been solved, giving an accurate picture of the dinuclear iron centers in these proteins [20-221. The sMMO hydroxylase has recently been crystallized and its spacc group reported, but the structure has yet to be refined [23]. It is the ligands in the first coordination sphere of the iron atoms that most influence the redox potentials and other properties which determine the function of the active sites in each of these iron-oxo proteins. The first coordination sphere of R2 consists of mainly oxygen-donating ligands while that of hemerythrin has mainly N-donor ligands. In the absence of an hydroxylase crystal structure, overlaying the gene sequence of sMMO [24] on that of R2 has resulted in a plausible picture of the binuclear iron center of the former [25]. The proposed hydroxylase site resembles that of R2 much more t...

show abstract

“…It is suggested that nonheme monooxygenase oxidation also includes the mononuclear (Fe v= O) or binuclear (FeW-O-Fe Iv= O for MMO) analogs of the heme complex [7,9]. However, it is difficult to realize a possibility of Fe = O formation in the MMO active center in the absence of cysteine thiolate co-action, which is determining in the case of cyt.…”

Section: What Can Be An Alternative For Fe = O In Ch 4 Activation?mentioning

confidence: 99%

“…First, different O donors, such as PhlO, NalO4, and t-BuOOH, which are active in the case of P-450 and its models, are inefficient in the case of MMO [7]. Although H202 can be used instead of O2/NADH [7,9], the oxidation of n-alkanes in this case is low efficient and has different C-H selectivity [7].…”

Section: What Can Be An Alternative For Fe = O In Ch 4 Activation?mentioning

confidence: 99%

See 1 more Smart Citation

The mechanism of methane and dioxygen activation in the catalytic cycle of methane monooxygenase

Shteinman

1995

FEBS Letters

View full text Add to dashboard Cite

Activation of the hydroxylase of sMMO from Methylococcus capsulatus (Bath) by hydrogen peroxide

Cited by 55 publications

References 45 publications

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Further Evidence for Multiple Pathways in Soluble Methane‐Monooxygenase‐Catalysed Oxidations from the Measurement of Deuterium Kinetic Isotope Effects

Abduction of iron(III) from the soluble methane monooxygenase hydroxylase and reconstitution of the binuclear site with iron and manganese

The mechanism of methane and dioxygen activation in the catalytic cycle of methane monooxygenase

Contact Info

Product

Resources

About