Hydrocarbon monooxygenase

Mueller and Miller (33) and Brodie et al. (34) were the first to show that enzymes in the microsomal fraction of rat liver could effectively oxidize xenobiotics. Comparable enzymes (aryl hydrocarbon monooxygenases) were later reported in the hepatic tissues of fresh water and marine fish by Creaven et al. (35) and Buhler and Rasmusson (36). Reconstituted hepatic microsomal systems require cytochrome P-450 for monooxygenase activity in both mammals (37) and fish (38,39). Bend et al. 

HYDROGEN TUNNELING HYDROCARBON MONOOXYGENASE HYDROGENASE Hydrogen bonding,... 

The combination of bis[(2,6-carboxyl-carboxylato)pyri-dine]iron(n) [Fe (DPAH)2] and O2 results in the rapid autoxidation of the iron complex and is essentially unreactive with hydrocarbon substrates (e.g. c-CeH ). However, the presence of excess PhNHNHPh gives a system that is a hydrocarbon monooxygenase (C-C6H12c-CeHuOH). The distribution of R H isomers from 2-Me-butane indicates a selectivity in the order =CH > =CH2 > -CH3 the relative reactivities per C H bond are 1.00, 0.29, and 0.05, respectively. With Fe (PA)2/HOOH Fenton chemistry in 1.8 1 py/HOAc, the relative reactivities are 1.00, 0.43, and 0.07, and the values for aqueous HO- are 1.00, 0.48, and 0.10. Thus, the reactive intermediate from the Fe (DPAH)2/02/PhNHNHPh system is more selective than Fenton-derived and free HO-. 

Others such as pig liver microsomal FAD-containing monooxygenase have to be isolated from tissue with very low yields141 or like hydrocarbon monooxygenase from Pseudomonas oleovorans 12 131 require several protein components and cofactors, substantially limiting the use of these enzymes for the production of oxidized sulfur compounds. 

Hydrocarbon monooxygenase from Pseudomonas oleovorans[7, 8> 12] also catalyzes the stereoselective sulfoxidation of methyl thioether substrates[131 with up to 80 % ee. The products obtained with this enzyme are probably of the R-configiration. 

Oesch, F. 1976. Differential control of rat microsomal aryl hydrocarbon monooxygenase and epoxide hydratase. J. Biol. Chem. 251(l) 79-87. 

When the py-HOAc solvent system is replaced by MeCN or 3 1 MeCN/py autoxidation to 23 is observed without oxidation of hydrocarbon substrates [150]. However, added PhNHNHPh makes the system act as a hydrocarbon monooxygenase, converting cyclohexane to cyclohexanol. The proposed explanation is that the superoxo complex (DPAH)2Fe(02) formed... 

Patel RN, CT Hou, AI Laskin, A Felix (1982) Microbial oxidation of hydrocarbons properties of a soluble monooxygenase from a facultative methane-utilizing organisms Methylobacterium sp. strain CRL-26. Appl Environ Microbiol 44 1130-1137. 

Hydrocarbon hydroxylases introducing oxygen into nonoxygenated rings Toluene, phenanthrene, pyrene monooxygenases Hydrocarbon epoxidases... 

Although monooxygenases can be involved in the degradation of toluene, there is a complex relation between toluene monooxygenase activity and the degradation of chlorinated hydrocarbons. 

Oldenhuis R, RLJM Vink, DB Janssen, B Witholt (1989) Degradation of chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b expressing soluble methane monooxygenase. Appl Environ... 

Although the exact mechanism of degradation at metabolic level for each compound or group of compounds is not well known, the involvement of extracellular oxidative enzymes such as LAC, MnP, LiP, and versatile peroxidase (VP) (see Tables 1 and 2 of Chap. 6) and intracellular monooxygenases as cytochrome P-450 is well documented for pollutants such as hydrocarbons, dyes, and halogenated solvents [25]. To determine the actual role of the extracellular enzymes, many studies are performed in vitro experiments with purified enzymes. In the case of cytochrome P-450, usually inhibitors are used. 

Table III. Inhibition of monooxygenase (aryl hydrocarbon hydroxylase) activity in fish and mammalian hepatic microsomes (based on...

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