Further studies on the activation of procollagenase, the latent precursor of bone collagenase. Effects of lysosomal cathepsin B, plasmin and kallikrein, and spontaneous activation.

TLDR: It is proposed that cathepsin B, kallikrein and plasmin may play a role in the physiological activation of latent collagenase and thus initiate degradation of collagen in vivo.

Abstract: 1 Cathepsin B, a tissue (lysosomal) proteinase, and two humoral proteinases, plasmin and kallikrein, activate the latent collagenase ('procollagenase') which is released by mouse bone explants in culture Other lysosomal proteinases (carboxypeptidase B, cathepsin C and D) and thrombin did not activate the procollagenase Dialysis of the culture fluids against 3M-NaSCN at 4 degrees C and, for some culture fluids, prolonged preincubation at 25 degrees C also caused the activation of procollagenase 2 In all these cases, activation of procollagenase involved at least two successive steps: the activation of an endogenous latent activator present in the culture fluids and the activation of procollagenase itself 3 An assay method was developed for the endogenous activator Human serum, bovine serum albumin, casein and cysteine inhibited the endogenous activator at concentrations that did not influence the collagenase activity N-Ethylmaleimide and 4-hydroxy-mercuribenzoate stimulated the endogenous activator, but iodoacetate had no effect 4 It is proposed that cathepsin B, kallikrein and plasmin may play a role in the physiological activation of latent collagenase and thus initiate degradation of collagen in vivo This may occur whatever the molecular nature of procollagenase (zymogen or enzyme-inhibitor complex) might be