Detoxication enzymes

Greulich, K., Hoque, E., and Pflugmacher, S., Uptake, metabolism, and effects on detoxication enzymes of isoproturon in spawn and tadpoles of amphibians, Ecotoxicol. Environ. Saf., 52, 256, 2002. 

Yu, S.J. Interactions of allelochemicals with detoxication enzymes of insecti-... 

Comparative biochemistry. Some researchers believe that the proper role of comparative biochemistry is to put evolution on a molecular basis, and that detoxication enzymes, like other enzymes, are suitable subjects for study. Xenobiotic-metabolizing enzymes were probably essential in the early stages of animal evolution because secondary plant products, even those of low toxicity, are frequently lipophilic and as a consequence would, in the absence of such enzymes, accumulate in lipid membranes and lipid depots. The evolution of cytochrome P450 isoforms, with more than 2000 isoform cDNA sequences known, is proving a useful tool for the study of biochemical evolution. 

Yu S. J. (1984) Interactions of allelochemicals with detoxication enzymes of insecticide susceptible and resistant fall armyworm. Pest. Biochem. Physiol. 22, 60-68. 

Krieger, R.I., Feeny, P.P., and Wilkinson, C.F., Detoxication enzymes in the guts of caterpillars A evolutionary answer to plant defenses, Science, 172,579,1971. 

Terriere, L.C., Induction of detoxication enzymes in insects, Annu. Rev. Entomol., 29, 71,1984. 

Yu, S.J. and Nguyen, S.N., Insecticide susceptibility and detoxication enzyme activities in per-methrin-selected diamondback moths, Pestic. Biochem. Physiol., 56, 69,1996. 

Fahey, J.W. and Talalay, R, Antioxidant functions of sulforaphane a potent inducer of phase II detoxication enzymes. Food Chem. Toxicol, 37, 973-979, 1999. Shapiro, T.A., Fahey, J.W., Wade, K.L., Stephenson, K.K., and Talalay, P. Chemo-protective glucosinolates and isothiocyanates of broccoh sprouts metabolism and excretion in humans. Cancer Epidemiol Biomarkers Prev., 10, 501-508, 2001. Faulkner, K., Mithen, R., and Williamnson, G., Selective increase of the potential anticarcinogen 4-methylsulphinylbutyl glucosinolate in broccoh. Carcinogenesis, 19, 605-609, 1998. 

Some of these differences can be attributed to variations in detoxication mechanisms. For example, the loss of consciousness induced in several species of laboratory animals by hexobarbital (a barbiturate derivative that depresses the central nervous system (CNS)) shows marked differences these are attributable to the activity of the detoxication enzyme that inactivates this chemical. In the mouse, the activity of the detoxifying enzyme is 16-fold greater than that in the dog, which is reflected by 12 min of hexobarbital-induced sleep in the mouse versus 315 min of sleep in the dog. There are other examples of species-related differences in the ability to detoxify chemicals that consequently result in differences in toxicity. Other examples include the industrial chemicals, ethylene glycol and aniline. Ethylene glycol is metabolized to oxalic acid, which is responsible for its toxicity, or to carbon dioxide. The rank order of ethylene glycol toxicity in animals is as follows cat rat rabbit this is the same for the extent of oxalic acid production. Aniline is metabolized in the cat and dog mainly to o-aminophenol, and these species are more prone to toxicity however, in the rat and hamster aniline is metabolized mainly to I-aminophenol and thus these species are less susceptible to aniline toxicity. 

Wiegand, C., S. Pflugmacher, M. Giese, H. Frank and C. Steinberg. Uptake, toxicity, and effects on detoxication enzymes of atrazine and trifluoroacetate in embryos of zebrafish. Ecotoxicol. Environ. Saf. 45 122-131, 2000. 

The conclusion of the study was that interindividual variations in the amount of human cytochrome 2A6 and 2E1 could contribute to the susceptibility of environmental procarcinogens including those derived from tobacco smoke. Cytochromes P-450 largely bioactivate nicotine and nicotine-related nitrosoamines to electrophilic materials. Presumably, the balance between bioactivating enzyme activity and detoxicating enzyme activity is important in determining the overall susceptibilities of humans to exposure to chemicals. Below, the properties of several additional enzymes in nicotine detoxication are described. 

Pflugmacher S, Wienke C, and Sandermann H, Activity of phase I and phase II detoxication enzymes in Antarctic and Arctic macroalgae, Mar. Environ, Res., 48, 23, 1999. 

In the 1970s compounds were developed which eliminated these harmful effects on the growth of crop plants. They can be applied for the treatment of the seeds or admixed with EPTC in a quantity of 5-10%. These antidotes or safener substances presumably exert their action by stimulating the functioning of the EPTC-detoxicating enzyme of crop plants, of glutathione-S-transferase. This theory is supported by the observation that sensitive and tolerant plants absorb and translocate EPTC to essentially the same extent, but in tolerant plants the active substance is rapidly metabolised oxidatively to sulfoxide, then to biologically inactive sulfon derivatives, while in sensitive plants this process is slower and the plant meanwhile dies. 

Accelerated detoxicating enzyme activity by Chlorella administration... 

Isman, M.B., Feng, R., Johnson, D.L., 1996. Detoxicative enzyme activites in five species of field-collected melanopline grasshoppers (Orthoptera Acrididae). Can. Entomol. 128, 353-354. 

Eahey JW, Talalay P. Antioxidant functions of sulforaphane a potent inducer of phase 11 detoxication enzymes. Pood Chem Toxicol 1999 37 973-979. 

Mixing pesticides with different modes of action and different detoxication patterns Switching life-stage target Increased sensitivity in resistant pests Inhibition of detoxication enzymes... 

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