Comparative action of cathepsins B and L on intramuscular collagen as assessed by differential scanning calorimetry

Intramuscular beef collagen of different degrees of reticulation was treated with cathepsin L obtained from chicken liver and a commercial cathepsin B prepared from beef spleen. It was shown that, in the absence of calcium, both proteinases caused a decrease in the initial temperature of denaturation whereas the total enthalpy of denaturation was unaffected. Treatment with cathepsin B resulted in the appearance of a new peak of denaturation at a lower temperature (≈ 44°C), a change wholly comparable with that obtained previously when intramuscular beef collagen was treated with a collagenase from Clostridium histolyticum. There was no such change with cathepsin L. The addition of 20 mM CaCl(2) to the incubation buffer brought about a shift in the total enthalpy of denaturation when collagen was treated with cathepsin L; in contrast, no additional effect was observed in cathepsin B treatments. These findings led to the suggestion that cathepsins B and L have a different mode of action on collagen and that there may be a similarity in the mechanism of action between cathepsin B and the bacterial collagenase.