Procathepsin K human

Procathepsin K is the inactive proenzyme of cathepsin K. Cathepsin K is a lysosomal cysteine protease and part of the papain cysteine protease family. It is expressed in osteoclasts. The gene encoding this protein is localized on human chromosome 1q21.

Cathepsin K has a role in bone resorption and remodeling. It has a triple helical collagen hydrolase activity. Mutations in the gene encoding this protein have been linked to pycnodysostosis.

Liquid (25 mM Tris pH 8.0, 500 mM NaCl)

Procathepsin K can be activated by adjusting the pH 4.0 by adding an equal volume of 100 mM NaAc pH 3.9, 10 mM DTT, 5 mM EDTA followed by incubation for 40 min at RT. Activated mature Cathepsin is highly auto-proteolytic at pH 4.0, and care must be taken to avoid self-proteolysis. If the activated enzyme is not used immediately, we recommend to add methyl methanthiosulfonate (1 mM final concentration; MeS-SO2Me; MMTS) and to freeze the sample in liquid nitrogen or on dry ice. The hydrophobic thiol-reactive compound MMTS modifies cysteine′s by attaching its relatively small, uncharged thiomethyl-blocking group to reactive sulfhydryl groups (Nishimura et al., 1975). This reversible reaction arrests the auto-proteolytic process. The activity of the enzyme can be restored to nearly unmodified levels by adding L-cysteine (3M excess over MMTS) to the enzyme solution.