Cyclooxygenase

Cyclooxygenase is an enzyme that is responsible for the key step in prostaglandin biosynthesis. Other names for this enzyme include: Prostaglandin-endoperoxide synthase (the current official name), Prostaglandin H2 synthase, and Prostaglandin G/H synthase. The enzyme is most commonly abbreviated "COX," but may also be referred to as "PTGS" or "PGHS." This enzyme is the therapeutic target for the nonsteroidal anti-inflammatory drugs (NSAIDs). Research has also revealed that it is present in most organisms in two isoforms. A constitutive COX-1 and an inducible COX-2. This article will refer to both isoforms as a single enzyme where appropriate, and will distinguish one from the other when necessary. Also, all information will refer to the human cyclooxygenases except where noted.

Structure and Function

Genomics and Structure

COX-1

The gene for COX-1 is located on the long arm of chromosome 9 at location 9q32-q33.3. After translation the enzyme contains 599 amino acids.

COX-2

The gene for COX-2 is located on the long arm of chromosome 1 at location 1q25.2-q25.3. After translation the enzyme contains 604 amino acids.

Function

Cyclooxygenase is responsible for the conversion of Arachidonic Acid to Prostaglandin H₂. Prostaglandin H₂ is the precursor to the series 2 prostanoids. Cyclooxygenase achieves this through the action of two active sites. First a cyclooxygenase active site (the source of the enzyme's common name) converts arachidonic acid to Prostaglandin G₂. Then a heme dependent peroxidase converts Prostaglandin G<sub2> to Prostaglandin H₂