Action of mammalian collagenases on type I trimer collagen

Type I trimer is a collagen species, which is synthesized by many cell types under abnormal conditions or when derived from pathologically altered tissues, and by embryonic cell types. In order to investigate the susceptibility of type I trimer to mammalian collagenases, renatured type I trimer and type I collagens were incubated with human fibroblast and neutrophil enzymes and enzyme degradation was followed by viscometry and by polyacrylamide gel electrophoresis. A comparison of reaction rates determined by viscometry revealed that the type I trimer was degraded at less than one-fifth the rate of type I collagen by both enzymes. The human fibroblast collagenase had Km values of 8.4 +/- 1.6 and 6.3 +/- 0.7 microM for the type I trimer and type I collagens, respectively. These values were not significantly different. However the type I trimer had a kcat value of 10.6 +/- 2.0/hour which was only one fifth of 51.2 +/- 5.5/hour obtained for the type I collagen. From these results we conclude that the type I trimer collagen is a poor substrate for the skin and PMN collagenases relative to type I.