Encyclopedia of Systems Biology

2013 Edition
| Editors: Werner Dubitzky, Olaf Wolkenhauer, Kwang-Hyun Cho, Hiroki Yokota

Phase II Enzymes

  • Vani BrahmachariEmail author
  • Shruti Jain
Reference work entry
DOI: https://doi.org/10.1007/978-1-4419-9863-7_866



The phase II reactions are usually involved in the conversion of  prodrug into inactive metabolites. They are involved in detoxication by interactions with the polar functional groups of phase I metabolites. Sites on drugs where conjugation reactions occur include carboxyl (−COOH), hydroxyl (−OH), amino (NH2), and sulfhydryl (−SH) groups. The products of these reactions have increased molecular weight as it involves addition of groups like methyl and acetyl groups. They are involved in the removal of metabolites from the body. A few examples are as follows:
  • Methylation: Thiopurine methyltransferase, TPMT

  • Sulphonation: Glutathione S-transferase, GST

  • Acetylation: N-acetyltransferase, NAT2


Copyright information

© Springer Science+Business Media, LLC 2013

Authors and Affiliations

  1. 1.Dr. B. R. Ambedkar Center for Biomedical Research, University of DelhiDelhiIndia