TIMPs-1 through -4 regulate the activity of zinc metalloproteases known as MMPs, ADAMs and ADAMTSs. Structurally, TIMPs contain two domains. The N-terminal domain binds to the active site of mature metalloproteases via a 1:1 non-covalent interaction, blocking access of substrates to the catalytic site. In addition, The C-terminal domain of TIMP-1 and TIMP-2 binds to the hemopexin- like domain of pro-MMP-9 and pro-MMP-2, respectively. The latter binding is essential for the cell surface activation of MMP-2 by MMP-14