Tissue kallikreins are a family of extracellular serine proteases consisting of 15 members. Tissue kallikreins have attracted great interest as potential biomarkers for various cancers, including prostate, ovarian, breast, testicular, and lung. Human Kallikrein 6 (hKLK6) is a member of tissue kallikrein family observed in breast and brain tissues, colon carcinoma cells, and oligodedrocytes. Known protein substrates of hKLK6 are myelin basic protein, the precursor of the A beta amyloid peptide, and plasminogen. Its physiological functions may include the participation in demyelination processes as well as in the progression of inflammatory disease of the CNS. The activity assay of recombinant mouse KLK6 was measured by its ability to cleave the fluorogenic peptide substrate Boc-QAR-AMC. The rmKLK6 was activated by Lysyl-endopeptidase in the activation buffer 50 mM Tris, 0.05% (w/v) Brij-35, pH 8.0, of which equal volumes of 200 ug/ml rmKLK6 and 2.5 mU/ml Lysyl-endopeptidase were combined and incubated at room temperature for 30 minutes. The activated rmKLK6 was diluted to 3 ug/ml in assay buffer and start the reaction by adding 50 μL of 200 μM substrate. Read at excitation and emission wavelengths of 380 nm and 460 nm (top read), respectively, in kinetic mode for 5 minutes. The specific activity of recombinant mouse KLK6 is >6000 pmol/min/μg.