Kallikrein 5 was originally described from the skin as an enzyme involved in turnover of the stratum corneum, and later cloned from human EST libraries as a Kallikrein like enzyme. The skin is known to contain trypsin like and chymotrypsin like proteinases of 32 kDa and 25 kDa respectively, and these were determined to be hK5 and hK7. Kallikrein 5 is found is greatest abundance in the skin, and also in the brain, with lesser signal in the kidney, lung, mammary gland, and testis. Human breast milk is reported to contain high levels of Kallikrein 5. Less stringent PCR detects hK5 in many tissues, and analysis of cell lines by Western blot shows that many cell lines make hK5.