Mixed function oxidase MFO

The CYP enzymes active in phase I reactions are often oxidases or hydroxylases, sometimes called mixed function oxidase (MFO). An oxidase enzyme introduces into the substrate (i.e. the unwanted compound) both atoms of an oxygen molecule whilst... 

The biotransformation systems involved in insecticide metabolism have been studied in the R and S populations to determine any differences which might be potential contributory factors to or results of insecticide resistance. In addition, the possibility of mixed-function oxidase induction has been investigated. Specifically, the studies have encompassed a seasonal study of microsomal mixed-function oxidase (mfo) components, and studies of aldrin, dieldrin and DDT metabolism. 

The marine environment acts as a sink for a large proportion of polyaromatic hydrocarbons (PAH) and these compounds have become a major area of interest in aquatic toxicology. Mixed function oxidases (MFO) are a class of microsomal enzymes involved in oxidative transformation, the primary biochemical process in hydrocarbon detoxification as well as mutagen-carcinogen activation (1,2). The reactions carried out by these enzymes are mediated by multiple forms of cytochrome P-450 which controls the substrate specificity of the system (3). One class of MFO, the aromatic hydrocarbon hydroxylases (AHH), has received considerable attention in relation to their role in hydrocarbon hydroxylation. AHH are found in various species of fish (4) and although limited data is available it appears that these enzymes may be present in a variety of aquatic animals (5,6,7,8). 

Few insects have been studied in detail in regard to the metabolism of insecticides by mixed function oxidases (MFO) (1). Most of those studies dealt with terrestrial insects. Information on the metabolism of insecticides by non-target aquatic insects is fragmentary. 

For foreign compounds, the majority of oxidation reactions are catalyzed by monooxygenase enzymes, which are part of the mixed function oxidase (MFO) system and are found in the SER (and also 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. 

We observed a protective effect of increased dietary protein on DMBA-induced breast tumor incidence when the diets varying in protein were fed prior to carcinogen administration. We have investigated the hypothesis that dietary protein may influence carcinogenesis via effects on the mixed-function oxidase (MFO) enzyme systems involved in carcinogen metabolism. 

Acrylonitrile owes some of its toxicity to cyanide generation, which inhibits cellular respiration. Preinduction of microsomal mixed function oxidase (MFO) with Arochlor 1254 greatly enhanced the toxicity of acrylonitrile and caused a threefold increase in cyanide levels in rats. Therefore, metabolic activation appears to be necessary in the toxicity of acrylonitrile. The direct reaction of acrylonitrile with the SH groups of proteins and its epoxide metabolite are also expected to be responsible for its effects. 

Dibenz[a,fi]anthracene is metabolically activated by the mixed function oxidase (MFO) system of the liver (P448) to form an epoxide that subsequently covalently binds to the DNA. This interaction with the DNA is believed to result in the carcinogenicity of the material. The particular area of the compound oxidized by the MFO system will result in epoxides of varying carcinogenic potency. 

PBO interferes with the detoxification of the insecticide by inhibiting the functions of the insects mixed function oxidase (MFO) enzymes (Casida. 1970) and plays an important role in preventing or delaying the onset of rcsislancc-... 

P-450-dependent mixed-function oxidases (MFO), which in the case of PAHs are called AHHs. AHH is an ubiquitous enzyme system and has been found in a variety of tissues including liver, lung, and gastrointestinal tract of rats, mice, hamsters, and monkeys. AHH has also been detected in human liver, lung, placenta, lymphocytes, monocytes, and alveolar macrophages (Singer and Grunberger... 

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