The action of cathepsin B and collagenolytic cathepsin in the degradation of collagen.

Cathepsin B and collagenolytic cathepsin were obtained from bovine spleen and human placenta and identified as thiol proteinases. Both enzymes degraded insoluble fibrous collagen maximally at pH 3.5 and soluble monomeric collagen near pH 4.5. The response to activators and inhibitors was similar for both enzymes. Collagenolytic cathepsin was unable to degrade the synthetic substrates of cathepsin B and was also shown to differ in its physico-chemical properties. Minor differences were noted in the action of these cathepsins on insoluble fibrous collagen from different tissues. It was concluded that the rate and extent of the dissolution of fibrous collagen was determined by the number and location of the interchain cross-links, the amount of the associated non-collagenous components and the type of solvent ions, but not by the collagen phenotype.