Cleavage of type I collagen by MMP-1 CAT domain, full-length MMP-1, MMP-12 CAT domain, and trypsin. Type I collagen (10 μg) was treated with 200 ng of enzyme in 50 mM Tris•HCl, pH 7.5, 150 mM NaCl, 5 mM CaCl2, 0.05% Brij35, 1 μM ZnCl2 for 36 h at either room temperature or 33 °C. Full-length MMP-1 (MMP1 FL) cleaved type I collagen at room temperature, resulting in the characteristic ¾ and ¼ fragments, while MMP-1 CAT domain (MMP1cat) showed a low level of hydrolysis and MMP-12 CAT domain (MMP12cat) did not cleave the collagen. At 33 °C, increased hydrolysis by MMP-1 CAT domain and a low level of hydrolysis by MMP-12 CAT domain was observed. Trypsin showed minimal collagen hydrolysis at either temperature. “Contr” is type I collagen alone.