Glucuronidation of xenobiotics

With some of the phase 2 metabolizing enzymes, there may be strict ontogenetic patterns of expression. Sulfate conjugation ability occurs early in rats, whereas glucuronidation (of xenobiotics), and conjugation with glutathione and amino acids, only develop over about 30 days from birth. 

The glucuronidation of bifirubin is discussed in Chapter 32 the reactions whereby xenobiotics are glu-curonidated are essentially similar. UDP-glucuronic acid is the glucuronyl donor, and a variety of glu-curonosyltransferases, present in both the endoplasmic reticulum and cytosol, are the catalysts. Molecules such as 2-acetylaminofluorene (a carcinogen), aniline, benzoic acid, meprobamate (a tranquilizer), phenol, and... 

The other primary Phase II metabolic pathway is glucuronidation, which involves the formation ofglucuronic acid conjugates of xenobiotics. This is catalyzed by a family of UDP-glucuronosyl transferases (UGTs) in the presence of uridine diphosphate... 

Ionizing Radiation. In general, ionizing radiation reduces the rate of metabolism of xenobiotics both in vivo and in enzyme preparations subsequently isolated. This has occurred in hydroxylation of steroids, in the development of desulfuration activity toward azinphosmethyl in young rats, and in glucuronide formation in mice. Pseudocholinesterase activity is reduced by ionizing radiation in the ileum of both rats and mice. 

Coffman BL, King CD, Rios GR, et al. The glucuronidation of opioids, other xenobiotics, and androgens by human UGT2B7Y(268) and UGT2B7H(268). Drug Metab Dispos 1998 26(l) 73-77. 

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