Corneal Collagenase: Specific Cleavage of Types (α1)2α2 and (α1)3Collagens

The susceptibility of various soluble collagens to rabbit corneal collagenase activity has been tested. The cleavage of the collagens has been assessed by gel electrophoresis and by electron microscopy of SLS crystallites precipitated by ATP. Collagens of both (α1)2α2 and (α1)3 chain types are cleaved at points 23.5 (± 0.5%) of the length of the molecule from the carboxy-terminus. Fractionation studies indicate that the same enzyme is responsible for the attack on both classes of collagen. These observations suggest that the amino-acid sequence or the structure defining the point of collagenase attack in the collagen molecule has been retained through phylogenetic development from the agnatha to primate species, and that more than one of the different classes of collagens distinguished in various vertebrate tissues can be degraded by the same enzyme.Evidence was obtained for the presence of an additional protease activity that was partly resolved from the collagenase by gel filtration. The other enzyme(s) caused loss of components and slowly degraded the large cleavage fragments produced by collagenase activity. It is suggested that the protease activity as well as the collagenase activity may mediate collagen degradation during corneal ulceration.