Prostaglandin-endoperoxide synthase 1 (COX-1) peroxidase site (COX-1 POX site)

The Prostaglandin-endoperoxide synthase 1 (COX-1) peroxidase site is a distinct catalytic domain within the bifunctional COX-1 enzyme, which is essential for the production of prostanoids [1]. This site contains a heme prosthetic group (protoporphyrin IX) and is responsible for the two-electron reduction of prostaglandin G2 (PGG2) to prostaglandin H2 (PGH2), the common precursor for thromboxanes and various prostaglandins [2]. Beyond its reductive role, the peroxidase site is critical for the activation of the cyclooxygenase site; it facilitates the formation of a tyrosyl radical (Tyr385) that initiates the oxygenation of arachidonic acid [3]. While most nonsteroidal anti-inflammatory drugs (NSAIDs) target the cyclooxygenase site, the peroxidase site is the primary locus for the inhibitory action of acetaminophen (paracetamol), which acts as a reducing agent to quench the catalytic radicals required for enzyme activity [4]. COX-1 is constitutively expressed in most tissues, where it maintains the gastric mucosa, regulates platelet aggregation, and supports renal blood flow [5]. Therapeutic targeting of this site is primarily used for analgesic and antipyretic effects, though it carries risks of gastrointestinal and renal side effects due to the systemic inhibition of protective prostaglandins [6].

Other names

PTGS1 peroxidase sitePGHS-1 peroxidase siteCyclooxygenase-1 peroxidase domainProstaglandin G/H synthase 1 peroxidase site

The peroxidase site reduces prostaglandin G2 to prostaglandin H2 and generates the tyrosyl radical necessary for cyclooxygenase activity; drugs like acetaminophen act as reducing agents at this site to inhibit the enzyme's catalytic cycle.