UNIT 4.30 Co-Oxidation by Cyclooxygenases

  1. Lawrence M. Szewczuk1,
  2. Trevor M. Penning2

Published Online: 1 NOV 2009

DOI: 10.1002/0471140856.tx0430s42

Current Protocols in Toxicology

Current Protocols in Toxicology

How to Cite

Szewczuk, L. M. and Penning, T. M. 2009. Co-Oxidation by Cyclooxygenases. Current Protocols in Toxicology. 42:4.30:4.30.1–4.30.14.

Author Information

  1. 1

    GlaxoSmithKline, Collegeville, Pennsylvania

  2. 2

    University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Publication History

  1. Published Online: 1 NOV 2009
  2. Published Print: NOV 2009


Cyclooxygenases (COXs; prostaglandin H2 synthases) catalyze the bis-dioxygenation of arachidonic acid (AA) to generate prostaglandin (PG) G2 followed by the peroxidative cleavage of PGG2 to yield PGH2, the precursor to all of the vasoactive PGs. These enzymes utilize a Fe-protoporhyrin IX (heme) co-factor to catalyze peroxide bond cleavage, which puts the Fe at a higher oxidation state (Fe3+ [RIGHTWARDS ARROW] Fe5+). The heme Fe requires two electrons (e) to return to its resting state (Fe3+) for the next round of catalysis. Peroxide bond cleavage thus occurs via compound I and compound II, observed for horseradish peroxidase. To return to Fe3+, electrons come from “co-reductants” and their subsequent oxidation by the enzyme is known as “co-oxidation”. The protocols in this unit are aimed at characterizing this side reaction of COXs. Curr. Protoc. Toxicol. 42:4.30.1-4.30.14. © 2009 by John Wiley & Sons, Inc.


  • peroxidase;
  • co-reductant;
  • co-substrate;
  • self-inactivation;
  • resveratrol;
  • phenol