In rheumatoid arthritis and osteoarthritis, the loss of extracellular matrix macromolecules, aggrecan and collagens exceeds new production, resulting in serious joint impairment. The primary cause of this loss is due to elevated proteolytic enzyme activities. Recent studies have suggested that the enzymes called 'aggrecanases' that specifically cleaves the Glu373-Ala 274 of the aggrecan core protein play a key role in the early phase of cartilage destruction. Two aggrecanases have been purifi...