Abstract
Recent studies have demonstrated that there are two isozymes of COX (PGHS), COX-1 and COX-2. The roles of COX-1 and COX-2 in PG synthesis under physiological and pathological situation remain unclear, though it has been recognized that COX-1 produces PGI2 in endothelium, TXA2 in platelets, and PGE2 in gastric mucosa. In this paper, we will demonstrate the regulation of gene expression and activity in COX-1, and the characteristics of COX-1 protein and also discuss the physiological meanings of COX-1. In intact cells, endogenous arachidonic acid is not converted by COX-1, but exclusively converted by COX-2. The reason will be demonstrated that the Km value for arachidonic acid in COX-1 is different from that in COX-2 in intact cells. This means COX-1 dose not act under physiological conditions, and both COX-1 and COX-2 are timed to act complementary to each other under pathological conditions.
