Glycosylation regulates turnover of cyclooxygenase-2

Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in the prostanoid biosynthesis pathway, converting arachidonic acid into prostaglandin H2. COX-2 exists as 72 and 74 kDa glycoforms, the latter resulting from an additional oligosaccharide chain at residue Asn580. In this study, Asn580 was mutated to determine the biological significance of this variable glycosylation. COS-1 cells transfected with the mutant gene were unable to express the 74 kDa glycoform and were found to accumulate more COX-2 protein and have five times greater COX-2 activity than cells expressing both glycoforms. Thus, COX-2 turnover appears to depend upon glycosylation of the 72 kDa glycoform.