Mono-oxygenase enzyme

GAC Granular activated carbon MBAS Methyl blue active substances MMO Methane mono-oxygenase enzyme MSW Municipal solid waste... 

Cytochrome P-450 enzymes have been isolated from a variety of mammalian tissues, insects, plants, yeasts and bacteria. The P-450 cytochromes (Gunter and Turner, 1991) are membrane bound mono-oxygenase enzymes which catalyse oxygen atom transfer to entrapped non-polar substrates. The binding of carbon monoxide to the enzyme produces a split in the 420 nm Soret band to give bands at 364 and 450 nm. The absorption at 450 nm distinguishes the hemoprotein from all others and hence provides... 

The hydrolytic and reductive capabilities of microorganisms, especially fungi, are extremely useful in evaluating the metabolic fate of drugs [18-21]. For instance, many pathways of oxidative reactions parallel the same ones in mammals. In addition, fungi have been shown to possess mono-oxygenase enzyme systems... 

The activation of dioxygen for the mono-oxygenation of saturated hydrocarbons by the methane mono-oxygenase enzyme systems (MMO hydroxylase/reductase) represents an almost unique biochemical oxygenase, especially for the transformation of methane to methanol. l The basic process involves the insertion of an oxygen atom into the C-H bond of the hydrocarbon via the concerted reduction of O2 by the reductase cofactor... 

For foreign compounds the majority of oxidation reactions are catalysed by mono oxygenase enzymes found in the SER and known as microsomal enzymes. Other enzymes involved in the oxidation of xenobiotics are found in other organelles such as the mitochondria and the cytosol. Thus amine oxidases located in the mitochondria, xanthine oxidase, alcohol dehydrogenase in the cytosol, the prostaglandin synthetase system and various other peroxidases may all be involved in the oxidation of foreign compounds. 

Inhibition of the cholinesterase enzymes depends on blockade of the active site of the enzyme, specifically the site which binds the ester portion of acetylcholine (figure 7.31). The organophosphorus compound is thus a pseudosubstrate. However, in the case of some compounds such as the phosphorothionates (parathion and malathion for example), metabolism is necessary to produce the inhibitor. In both cases metabolism by the microsomal mono-oxygenase enzymes occurs in which the sulphur atom attached to the phosphorus is replaced by an oxygen (figure 5,10). 

Oxidations. Most oxidative processes take place in liver microsomes and are catalysed by mono-oxygenase enzymes known as mixed-function oxidases. These processes require reduced nicotinamide-adenine dinucleotide phosphate, molecular oxygen and a complex of enzymes in the endoplas-matic reticulum. The terminal oxidizing enzyme is cytochrome P450, a hemoprotein. The notation P450 refers to the ability of the reduced (ferrous) form of the hemoprotein to react with carbon monoxide, yielding a complex with absorption peak at 450 nm. For each molecule... 

Mono-oxygenase enzymes and their simulation. A. A. Akhrem, D. I. Metelitsa and M. E. Skurko, Russ. Ghent. Rev. (Engl. TransL), 1975, 44, 398-412 (193). 

The ubiquitous cytochromes P-450, found in plants, animals, yeast, and bacteria [20-29], are mono-oxygenase enzymes. They catalyze the oxygenation of... 

Carbonyl oxides e.g. (8), produced via singlet oxygen oxidation of diazo-compounds, can epoxidize olefins. It is considered that such intermediates can serve as useful chemical models for the mono-oxygenase enzymes. 

Mono oxygenases, enzymes that transfer one oxygen atom to the substrate from molecular oxygen, and dioxygenases, enzymes that transfer both oxygen atoms from molecular oxygen, have been used for oxidations. Examples of such reactions are shown in Fig. 10.17. ... 

The photo-excited states of some inorganic complexes are able to abstract an H atom from alkanes. Finally, high-oxidation-state late transition-metal oxo complexes snch as the active Fe =0 or Fe -0 species of cytochrome P450 methane mono-oxygenase enzyme, are also able to abstract an H atom from alkanes, which then leads to their hydroxylation (see Chap. 18). It is also possible, in some cases, to remove an H atom from Hj (see Chap. 15) ... 

This mechanism represents a shortcut in biological mono-oxygenase enzyme systems that use O2 as oxygen atom sources and whose mechanism is much more complex because of the requirement to cleave O2. Non-porphyrinic binuclear methane mono-oxygenase model complexes are also able to activate methane in the same way (see Chap. 19). When S = RH, Groves originally proposed the well-known rebound mechanism in which the Fe =0 species removes an H atom from RH, then transfers OH to produce the alcohol ROH ... 

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