Provided below are ELISA kits targeting cathepsin K, a human protein encoded by CTSK. This protein is 329 amino acids long, with a mass of 37 kDa, and is a member of the Peptidase C1 family. There is a noted implication in Pycnodysostosis. Other alias names for this protein include: cathepsin O1, cathepsin O2, cathepsin X, CTS02, PKND, and PYCD. ELISA kits are available that are reactive to human, mouse, rat, bovine, chicken, primate, guinea pig, fish, plant, and other mammalian variants of the target antigen.