UNIT 4.30 Co-Oxidation by Cyclooxygenases
Published Online: 1 NOV 2009
Copyright © 2009 by John Wiley & Sons, Inc.
Lab Protocol Title
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.
- Published Online: 1 NOV 2009
- 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+ 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.