THE STRUCTURAL BASIS FOR THE ELASTOLYTIC ACTIVITY OF THE 92-KDA AND 72-KDA GELATINASES

Several matrix metalloproteinases, including the 92-kDa and 72-kDa gel atinases, macrophage metalloelastase (MME), and matrilysin degrade ins oluble elastin. Because elastolytically active MME and matrilysin cons ist only of a catalytic domain (CD), we speculated that the homologous CDs of the 92-kDa and 72-kDa gelatinases would confer their elastolyt ic activities. In contrast to the MME CD, the 92 and 72 CDs expressed in Escherichia coli (lacking the internal fibronectin type II-like rep eats) had no elastase activity, although both were gelatinolytic and c leaved a thiopeptolide substrate at rates comparable to the full-lengt h gelatinases. To test the role of the fibronectin type II-like repeat s in elastolytic activity, we expressed the 92-kDa gelatinase CD with its fibronectin type II-Like repeats (99 CD/FN) in yeast. 92 CD/FN deg raded insoluble elastin with activity comparable to full-length 92-kDa gelatinase. 92 and 72 CDs lacking the fibronectin type II-like repeat s did not bind elastin, whereas the parent enzymes and 92 CD/FN did bi nd elastin. Furthermore, recombinant 92-kDa fibronectin type II-like r epeats inhibited binding of the 92-kDa gelatinase to elastin. We concl ude that the 92- and 72-kDa gelatinases require the fibronectin type I I-like repeats for elastase activity.