| The prostanoid family includes PGD2, PGE2, PGF2alpha, PGI2, thromboxane A2 and prostaglandins. The prostaglandins (PGs) are implicated in various physiological and pathophysiological events, including male fertility, menstruation, ovulation, pregnancy, implantation and inflamatory and neoplastic diseases. The biosynthesis of PGs and some other prostanoids, is catalyzed in a rate limiting step by PG-H synthase (also known as cyclooxygenase (COX), PG-endoperoxidase synthase (PTGS)) which converts arachidonic acid to prostaglandin/prostanoid precursor PGH2. Two cyclooxygenase isozymes, COX1 (human, 576aa, 69-72kD, chromosome 9) and COX2 (human, 604aa, 74kD, chromosome 1) have been identified. COX1, a constitutively expressed isoform, produces physiologically relevant prostanoids such as those in stomach and platelets. COX2 isoform is inducible and rapidly upregulated at inflamation sites and forms proinflamatory prostanoids. The overexpression of COX-2 also leads to tumerogenesis. Recently, a third isoform COX3 (canine 633aa, ~65kD in human aorta) has been reported. Two smaller COX1-derived proteins (partial COX1) PCOX1a (canine 414aa, ~53kD in human aorta) and PCOX1b have also been characterized. The COX3, but not PCOX1a, possesses glycosylation dependent cyclooxygenase activity. The nonsteroidal antiinflammatory drugs (NSAIDs) reduce the formation of prostaglandins by inhibiting the activity of cyclooxygenases (COX1, COX2 and COX3), This ability was associated with inhibition of COX, which converts arachidonic acid to the prostaglandin precursor prostaglandin H2. Molecular Weight: 70-74kD/subunit (Homodimer) Enzyme Activity: ~9200units/ml. As determined by the oxygen consumption assay. Specific Activity: 8000 units/mg protein. Unit Definition: One unit of enzyme consumes one nmol of oxygen per minute at 37C in 0.1M Tris-HCl buffer, pH 8.0, 100uM arachidonate, 5mM EDTA, 2mM phenol, and 1uM hematin. Storage and Stability: Aliquot to avoid repeated freezing and thawing and freeze at -70C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Aliquots are stable for 6 months after receipt. The enzyme preparation contains diethyldithiocarbamate (DDC) as a preservative. If this preservative is undesirable, it can be removed by standard desalting procedures. However, the enzyme is extremely unstable in the absence of the preservative and should be used within one hour. |
