Triple Point Biologics' Cysteine Proteinases antibody catalog covers the major papain-fold cysteine proteases, calpain isoforms, and deubiquitinating enzymes represented in mammalian tissues, including cathepsins B, F, H, K, L, O, S, V, and W, calpain-1 and -2, granzyme B, and selected USP-family members. Cysteine proteinases share a conserved catalytic dyad (Cys–His) and act across a wide range of biological compartments: cathepsins B, L, H, F, O, S, V, and W are predominantly lysosomal hydrolases involved in bulk protein turnover and antigen processing; cathepsin K is a collagenolytic enzyme expressed at high levels in osteoclasts and central to bone matrix remodeling; calpains are calcium-regulated cytosolic proteases that modulate cytoskeletal organization and apoptotic signaling; and granzyme B, a serine-fold outlier sometimes grouped here by substrate mechanism, is a serine protease secreted by cytotoxic T lymphocytes that cleaves caspase substrates to initiate target-cell death. Dysregulation of these enzymes is documented in osteoporosis, lysosomal storage disorders, neurodegenerative pathology, tumor invasion, and immune evasion, making them high-priority research targets across multiple disease models.

Triple Point Biologics has produced antibodies against proteinases and their inhibitors continuously since 1994. Each rabbit polyclonal in this collection is raised against a defined antigen region — typically a recombinant domain spanning the mature processed form of the protease — and lot-qualified by Western blot on cell lysate or recombinant protein and by immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections. Immunofluorescence validation data are provided where subcellular localization is relevant (e.g., lysosomal cathepsins, cytosolic calpain). Epitope coordinates and predicted or experimentally confirmed cross-reactivity to mouse, rat, and human orthologues are documented in each product datasheet. Every antibody target in this collection has a matched recombinant protein produced in the same laboratory, enabling use as a positive control on the same blot or section and removing a common source of false-negative ambiguity. Species cross-reactivity is stated as "validated" only when confirmed by direct testing, or "predicted" based on antigen sequence identity ≥ 85%.

Documented applications for this antibody collection include detection of endogenous protease expression and processing-state isoforms by Western blot, spatial localization in tissue sections by IHC (osteoclast cathepsin K in decalcified bone, tumor-infiltrating cathepsin B in carcinoma sections, granzyme B in lymphoid tissue), co-localization with lysosomal markers by IF, and use as capture or detection reagents in sandwich ELISA formats. For experimental design guidance, the protease activity assay guide covers substrate selection and inhibitor controls; the recombinant protein positive controls guide details how matched recombinants are incorporated into antibody validation workflows; and the protease inhibitor screening guide addresses assay formats relevant to cysteine protease drug discovery. Full validation documentation for each lot is available at Quality and Validation.