Xenobiotic metabolizing

Xenobiotics metabolism, 1, 223-225 monooxygenation cytochrome P450 in, 1, 259-260 Xenon... 

Microbial Transformations and Interactions with the Xenobiotic Metabolizing Enzyme (XME) System... 

Figure 3 Some interactions between gastrointestinal bacteria and the xenobiotic metabolizing enzyme system of the host. Solid lines, host XME system reactions dotted lines, classes of reactions mediated by gastrointestinal bacteria. Specific examples of reaction classes 1-5 are cited in the text. (Modified from Rowland and Tanaka " )...

FIGURE S.45 (o) Mechanism of induchon of xenobiotic metabolism caused by TCOO and pofyt/C ... 

Lodovici M, Aiolli S, Monserrat C, et al. 1994. Effect of mixture of 15 commonly used pesticides on DNA levels of 8-hydroxy-2-deoxyguanosine and xenobiotic metabolizing enz5mies in rat liver. J Environ Pathol Toxicol and Oncol 13 163-168. 

For an account of the main types of enzymes involved in xenobiotic metabolism, see Jakoby (1980). 

Apart from monooxygenases, other enzymes concerned wih xenobiotic metabolism may also be induced. Some examples are given in Table 2.5. Induction of glucuronyl transferases is a common response and is associated with phenobarbital-type induction of CYP family 2. Glutathione transferase induction is also associated with this. A variety of compounds, including epoxides such as stilbene oxide and... 

Jakoby, W.B. (1990). Although a little out of date, still a useful source on the enzymes concerned with xenobiotic metabolism. 

Livingstone, D.R. (1991). Organic xenobiotic metabolism in marine invertebrates. In R. Gilles (Ed.) Advances in Comparative and Environmental Physiology 7, 46-185. 

Ekins S, Wrighton SA. The role of CYP2B6 in human xenobiotic metabolism. Drug Metab Rev 1999 31 719-54. 

Talafous J, Sayre LM, Mieyal JJ, Klopman G. META. 2. A dictionary model of mammalian xenobiotic metabolism. J Chem Inf Comput Sci 1994 34 1326-33. Klopman G, Tu M, Talafous J. META. 3. A genetic algorithm for metabolic transform priorities optimization. J Chem Inf Comput Sci 1997 37 329-34. Langowski J, Long A. Computer systems for the prediction of xenobiotic metabolism. Adv Drug Del Rev 2002 54 407-15. 

Yang CS, Brady JF, Hong JY Dietary effects on cytochromes P450, xenobiotic metabolism, and toxicity. FASEB J 1992 6 737. 

Glutathione has other important functions in human cells apart from its role in xenobiotic metabolism. 

Intake of various xenobiotics such as phenobarbital, PCBs, or certain hydrocarbons can cause enzyme induction. It is thus important to know whether or not an individual has been exposed to these inducing agents in evaluating biochemical responses to xenobiotics. Metabolites of certain xenobiotics can inhibit or stimulate the activities of xenobiotic-metabolizing enzymes. 

SOHN O S, SURACE A, FIALA E S, RICHIE J P, COLOSIMO S, ZANG E and WEISBURGER J H (1994) Effects of green and black tea on hepatic xenobiotic metabolizing systems in the male F344 mt , Xenobiotica, 24, 119-27. 

To date, there is very little known about if and how phytochemicals modulate the metabolism of GIT tissues other than the liver. Of particular interest are the xenobiotic metabolizing enzymes of the GIT, which are involved with transformation of drugs and toxins. Whereas the metabolic activities of the resident microflora dominate in the large intestine, mucosal enzyme activities are more important in the small intestine where bacterial densities are lower and the villi and microvilli increase the area of exposure. 

Studies on rats had shown no toxicity of astaxanthin preparations. Dietary administration of astaxanthin has proved to significantly inhibit carcinogenesis in the mouse urinary bladder, rat oral cavity, and rat colon. In addition, it is reported to induce xenobiotic-metabolizing enzymes in rat liver. 

Gradelet, S. et al., Effects of canthaxanthin, astaxanthin, lycopene and lutein on Ever xenobiotic-metabolizing enzymes in the rat, Xenobiotica, 26, 49, 1996. 

Donnarumma L, G de Angelis, F Gramenzi, L Vittozzi (1988) Xenobiotic metabolizing enzyme systems in test fish. III. Comparative studies of liver cytosolic glutathione S-transferases. Ecotoxicol Environ Saf 16 180-186. 

Sariaslani FS (1991) Microbial cytochromes P-450 and xenobiotic metabolism. Adv Appl Microbiol 36 133-177. 

R Kato, RW Eastbrook, MN Cayen. Xenobiotic Metabolism and Disposition. London Taylor Francis, 1989, p 109. 

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