Clostridial collagenases are among the most efficient degraders of eukaryotic collagen known; saprophytes use collagen as a carbon source while pathogens additionally digest collagen to aid in host colonization. Has both tripeptidylcarboxypeptidase on Gly-X-Y and endopeptidase activities; the endopeptidase cuts within the triple helix region of collagen while tripeptidylcarboxypeptidase successively digests the exposed ends, thus clostridial collagenases can digest large sections of collagen (By similarity). Digestion of native collagen in the triple helical region at Xaa-|-Gly bonds. With synthetic peptides, a preference is shown for Gly at P3 and P1', Pro and Ala at P2 and P2', and hydroxyproline, Ala or Arg at P3'. Binds about 6 Ca(2+) per subunit (Probable). The metallopeptidase and PKD domains bind 1 Ca(2+), while CDB binds 2 (Probable). Binds 1 zinc ion. The mature protein has 4 domains; a metalloprotease domain (S1, approximately residues 87-761), S2 (762-860, equivalent to PKD), and 2 collagen-binding domains S3a (865-979) and S3b (992-1104) (PubMed:9922257). The metalloprotease S1 domain is composed of 3 subdomains which together resemble a saddle; an activator domain (residues 93-367), the catalytic peptidase subdomain (377-646) and a helper subdomain (654-767) (By similarity). Clostridial collagenases enable the bacteria to infiltrate and colonize host tissue, and contribute to gas gangrene (myonecrosis) pathogenesis. Belongs to the peptidase M9B family. Collagenase subfamily.