RT Book, Section A1 Parkinson, Andrew A1 Ogilvie, Brian W. A2 Klaassen, Curtis D. A2 Watkins, John B. SR Print(0) ID 6480095 T1 Chapter 6. Biotransformation of Xenobiotics T2 Casarett & Doull's Essentials of Toxicology, 2e YR 2010 FD 2010 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-162240-0 LK accesspharmacy.mhmedical.com/content.aspx?aid=6480095 RD 2024/03/28 AB Biotransformation is the metabolic conversion of endogenous and xenobiotic chemicals to more water-soluble compounds.Xenobiotic biotransformation is accomplished by a limited number of enzymes with broad substrate specificities.Phase I reactions involve hydrolysis, reduction, and oxidation. These reactions expose or introduce a functional group (—OH, —NH2, —SH, or —COOH), and usually result in only a small increase in hydrophilicity.Phase II biotransformation reactions include glucuronidation, sulfonation (more commonly called sulfation), acetylation, methylation, and conjugation with glutathione (mercapturic acid synthesis), which usually result in increased hydrophilicity and elimination.