Correlation of collagenase domain structure with functional assessment of collagenase: Historically, two broad categories of biochemical assays have been used for the characterize collagenase enzymes: assessment of enzyme functional activity by measuring the conversion of substrate to product or physical analysis of enzyme preparations. Collagenase activity was assessed by two broad classes of substrates: peptide substrates or macromolecular substrates that use native and denatured collagen. The most commonly used peptide substrates are the Pz and FALGPA peptides. The Pz peptide is used in the Wunsch assay. These assays are easy to perform, relatively consistent and are the primary assays many suppliers use to characterize collagenase products. The major disadvantages of these assays are they are biased to detect C2 as noted above. Further studies by Matsushita’s laboratory have shown that both degraded (no CBD) and intact C2 (1 CBD) are equivalent in degrading peptide substrates. These data are further supported by studies performed at VitaCyte that showed treatment of purified C1 or C2 with chymotrypsin resulted in > 85% loss of collagen degradation activity (CDA) when compared to untreated control. In contrast, only 7% of the Wunsch activity was lost when this same comparison was made.