Friends or Foes: Matrix Metalloproteinases and Their Multifaceted Roles in Neurodegenerative Diseases

Table 1

Classification and structure of MMPs.

Family	MMPs	Structure
Gelatinases	MMP-2, MMP-9	Signal peptide, propeptide, catalytic domain with fibronectin type II motif repeats, hinge region, and hemopexin domain
Matrilysins	MMP-7, MMP-26	Signal peptide, propeptide, and a catalytic domain
Archetypal MMPs	Stromelysins; MMP-3, MMP-10	Signal peptide, propeptide, a catalytic domain, hinge region, and a hemopexin domain
	Collagenases; MMP-1, MMP-8, MMP-13, MMP-18
	Other; MMP-12, MMP-19, MMP-20, MMP-27
Furin-activatable MMPs	Secreted; MMP-11, MMP-21, MMP-28	Signal peptide, propeptide, furin recognition motif, a catalytic domain, hinge region, and a hemopexin domain
	Type-I transmembrane; MMP-14 (MT1-MMP), MMP-15 (MT2-MMP), MMP-16 (MT3-MMP), and MMP-24 (MT5-MMP)
	Type-II transmembrane; MMP-23
	GPI-anchored; MMP-17 (MT4-MMP), MMP-25 (MT6-MMP)

GPI, glycosylphosphatidylinositol; MMP, matrix metalloproteinase.