“…MMP-9 is secreted as an inactive 92-kDa proenzyme and is activated to 83-kDa mature enzyme [ [178] , [194] , [260] , [261] , [262] ]. The pro-MMP-9 is comprised of four domains such as a signal peptide, the amino-terminal propeptide, the zinc-binding catalytic domain with three fibronectin type II repeats, and the carboxy-terminal hemopexin domain [ [255] , [258] , [263] , 264 , 188 ]. The activation of MMP-9 is mediated through the action of serine proteases, plasmin, or other MMPs such as MMP-3, plasminogen/MMP-3 complex, a complex of pro-MMP-9 and TIMP-1 by the removal of the prodomain and after activation it becomes involved in different physiological processes including the degradation of ECM proteins [ 178 , 179 ].…”