Oxygenation methane monooxygenase

In one study, a coarse-grained sand aquifer was injected with methane and oxygen to stimulate the production of methane monooxygenase (MMO) enzyme which is capable of degrading TCE (18). TCE, added at 60—100 )-lg/L, was degraded by 20—30%. Injected concentrations of methane and oxygen were approximately 20 mg/L and 32 mg/L, respectively. 

Methane monooxygenase is a classic monooxygenase in which two reducing equivalents from NAD(P)H are utilized to split the O—O bond of O2. Later, one oxygen atom is reduced to water while the second oxygen atom is incorporated into the substrate to yield methanol [42-45],... 

OXYGEN, OXIDES 0X0 ANIONS METHANE MONOOXYGENASE Methanol, autoprotolysis constant, AUTOPROTOLYSIS METHANOL DEHYDROGENASE... 

Fig. 14. Intermediates in the activation of oxygen by binuclear iron centers. Hr, Heme-rythrin RNR, ribonucleotide reductase MMO, methane monooxygenase.

Proteins with dinuclear iron centres comprise some well studied representatives like ribonucleotide reductase (RNR), purple acid phosphatase (PAP), methane monooxygenase hydroxylase (MMOH), ruberythrin and hemerythrin. The latter is an oxygen carrier in some sea worms it has been first characterized within this group and has thus laid the foundation to this class of iron coordination motif. Ruberythrin is found in anaerobic sulfate-reducing bacteria. Its name implies that, in addition to a hemerythrin-related diiron site another iron is coordinated in a mononuclear fashion relating to rubredoxin which is an iron-... 

Colby, J., D. I. Stirling, and H. Dalton, The soluble methane monooxygenase from Methylococcus copsulatus bath - Its ability to oxygenate n-alkanes, ethers and alicyclic, aromatic, and heterocyclic compounds , Biochem. J., 165, 395-402 (1977). 

Que L Jr, Dong YH. Modeling the oxygen activation chemistry of methane monooxygenase and ribonucleotide reductase. Acc Chem Res. 1996 29 190-6. 

Ruzicka, F., Huang, D-S., Donnelly, M L, and Frey P.A. (1990) Methane monooxygenase catalyzed oxygenation of of 1, 1-dimethylcyclopropane. Evidence for radical and carbocationic intermediates, Biochemistry 29, 1696-1700. s... 

Stahl, S.S., Fransicsco, W. A., Merkx, M., Klinman, J.P., and Lippard, S.J. (2001) Oxygen kinetic isotope effects in soluble methane monooxygenase, J. Biol. Chem. 276,4549-4553. 

Methane monooxygenase consists of a catalytically active diiron center. In the presence of oxygen this enzyme oxidizes methane and other hydrocarbons, i.e. molecules without any anchor-... 

Some of the first catalytic model systems for the simulation of the function of methane monooxygenase comprise monomeric as well as dimeric iron-containing model complexes bearing hydro-tris(pyrazolyl)borate ligands [6]. These complexes, e.g. 3, catalyze the oxidation of aromatic and aliphatic carbon-hydrogen bonds in the presence of oxygen (1 atm), acetic acid and zinc powder at room temperature (Scheme 2). 

Some preparations of iron exchanged into zeolite H-MFI by vapor-phase FeCL are known to be active and selective catalysts for the reduction of NO, with hydrocarbons or ammonia in the presence of excess oxygen and water vapor (45,46). The active centers in Fe/MFI are assumed to be binuclear, oxygen-bridged iron complexes, as follows from H2-TPR, CO-TPR, and ESR data (45,47) and EXAFS and XANES results (48,49). These complexes are structurally similar to the binuclear iron centers in methane monooxygenase enzymes that are employed by methanotrophic bacteria in utilization of methane as their primary energy source (50). It is believed that molecular oxygen reacts with these centers to form peroxide as the initial step in this chemistry (50). 

Andersson, K. K., Eroland, W. A., Lee, S.-K., and Lipscomb, J. D., 1991, Dioxygen independent oxygenation of hydrocarbons by methane monooxygenase hydroxylase component. New J. Chem. 15 411n415. 

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