Triple Point Biologics' Cysteine Proteinases recombinant catalog covers more than twenty members of this mechanistic class, including cathepsins B, F, H, K, L, O, S, V, and W; calpain-1 and -2; calpastatin-derived substrates; granzyme B; and multiple ubiquitin-specific protease (USP) family members. Cysteine proteinases share a conserved active-site Cys–His catalytic dyad and are unified by their sensitivity to thiol-alkylating agents and covalent epoxide- or nitrile-based inhibitors. Biologically, the class spans compartments: lysosomal cathepsins operate at acidic pH and are central to bulk proteolysis, antigen processing, and extracellular matrix remodeling; cytosolic calpains are calcium-activated and involved in cytoskeletal reorganization and signal transduction; and nuclear/cytosolic deubiquitinases of the USP family regulate protein turnover through ubiquitin chain editing. Cathepsin K has been extensively characterized in published studies of osteoclast-driven bone resorption; cathepsin B is frequently investigated in models of lysosomal membrane permeabilization associated with neurodegeneration and tumor invasion; granzyme B is a canonical effector protease examined in cytotoxic T-lymphocyte and NK-cell biology.

All recombinant cysteine proteinases in the TPB catalog are expressed in HEK293 cells to support native disulfide bonding and glycosylation patterns where relevant, and are supplied as either the mature processed form or the full-length zymogen as annotated per target. Each recombinant protein is paired with a matched rabbit polyclonal antibody produced in-house from the same antigen — a practice maintained since TPB began manufacturing proteinase and inhibitor antibodies in 1994. Antibodies are validated for Western blot and immunohistochemistry (IHC); cross-reactivity with non-human orthologues is designated as validated or predicted based on species-specific immunogen alignment data, never inferred generically.

Typical laboratory applications include fluorogenic substrate cleavage assays (e.g., Z-FR-AMC for cathepsin B/L, Ac-IEPD-AMC for granzyme B), active-site titration with E-64 or cystatin C, and use as positive controls in cell lysate immunodetection workflows. For assay design considerations, see the TPB guide to protease activity assays. For recommended loading concentrations and buffer compatibility when using recombinant proteins as immunoblot standards, refer to the recombinant protein positive controls guide. All catalog entries include the expressed domain boundaries, host cell line, tag configuration, and extinction coefficient to support accurate quantification.