Rat tail collagen type I was gelled at 2 mg/ml and incubated at 37 °C for 24 hours with enzymes in 12.5 mM Na PO4 buffer, pH 7.5. Panel A. Lane: 1) 1.5 μg MMP-1; 2) 1.5 μg MMP-1, 2 μg APCE; 3) 1.5 μg MMP-1, 4 μg APCE; 4) 1.5 μg MMP-1, 8 μg APCE; 5) 1.5 μg MMP-1, 12 μg APCE; 6) 1.5 μg MMP-1, 16 μg APCE; 7) 16 μg APCE. Panel B. Lane: 1) 1.5 μg MMP-1; 2) 1.5 μg MMP-1, 2 μg rFAP; 3) 1.5 μg MMP-1, 4 μg rFAP; 4) 1.5 μg MMP-1, 8 μg rFAP; 5) 1.5 μg MMP-1, 12 μg rFAP; 6) 1.5 μg MMP-1, 16 μg rFAP; 7) 16 μg rFAP. Digests were reduced and analyzed by 4–12% SDS-PAGE. Where present, the ~97 kDa band is either APCE or rFAP.