ABSTRACT
Experimental and clinical data collected over the last 25 years indicate that the anti-inflammatory, antipyretic, and analgesic properties of aspirin, ibuprofen, and other nonsteroidal anti-inflammatory drugs result from their ability to block prostaglandin (PG) synthesis. Prostaglandin endoperoxide H synthase (PGHSs) catalyze the conversion of arachidonate to PGH2. These enzymes have two activities: a cyclooxygenase activity that incorporates two molecules of oxygen into arachidonate to form PGG2 and a peroxidase activity that reduces the 15-hydroperoxide group of PGG2 to form PGH2. PGHSs are membrane proteins, and therefore preparation of microsomal membranes is a simple way to purify the enzymes partially before use in inhibitor assays. While not absolutely essential, isolation of membranes results in about a tenfold purification of PGHSs, and removes many of the soluble and nuclear proteins that may interfere with measurements of cyclooxygenase activity and determinations of inhibition constants.
