Acting on peptide bonds (peptidases);
Digestion of native collagen in the triple helical region at !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'
Six species of metalloendopeptidase acting on native collagen can be isolated from the medium of Clostridium histolyticum. Class I has forms alpha (68 kDa), beta (115 kDa) and gamma (79 kDa); class II has delta (100 kDa), epsilon (110 kDa) and zeta (125 kDa). The two classes are immunologically crossreactive, but have significantly different sequences, and different specificities such that their actions on collagen are complementary. The enzymes also act as peptidyl-tripeptidases. Variants of the enzyme have been purified from Bacillus cereus , Empedobacter collagenolyticum , Pseudomonas marinoglutinosa , and species of Vibrio, Vibrio B-30 (ATCC 21250)  and V. alginolyticus (previously Achromobacter iophagus) [3,8]. Also known from Streptomyces sp. . The Vibrio enzyme is the type example of peptidase family M9.
EC 18.104.22.168 created 1961 as EC 22.214.171.124, transferred 1972 to EC 126.96.36.199 (EC 188.8.131.52 created 1978, incorporated 1992, EC 184.108.40.206 created 1972, incorporated 1978)