The human tissue Kallikrein gene family encodes 15 serine proteases. All Kallikreins share structural similarities including cysteine residues, a catalytic triad of His, Asp and Ser residues, typically five coding exons, and varied intron phases. Kallikreins are predominantly secreted as inactive zymogens prior to activation by cleavage of an N-terminal peptide and all function extracellularly. Kallikreins can be activated autocatalytically, via other Kallikreins, or additional proteases. While structurally similar, Kallikrein family members have distinct functions and have key roles in many physiological and pathological processes. Many human tissue Kallikreins also show promise as cancer biomarkers, which may facilitate earlier detection and characterization of many forms of cancer. 


Kallikrein 14, also known as kallikrein-like6 (KLK-L6), is a trypsin-like serine proteinase. Kallikrein 14 was discovered by cloning the kallikrein locus on chromosome 19 and was found to be similar to the other kallikrein family genes. Kallikrein 14 is produced by a number of tissues, including the brain, spinal cord, esophagus, salivary gland, breast, prostate, uterus, lung, thymus and thyroid. Like many of the kallikreins, Kallikrein 14 is also found in biological fluids like serum, breast milk, amniotic fluid, seminal plasma and cerebrospinal fluid. Kallikrein 14 message has been reported to be decreased in some breast cancers and in ovarian cancers, similar to Kallikrein 10. Some cell lines express Kallikrein 14 in culture and like many of the kallikreins, the production is stimulated by hormones. Recombinant kallikrein 14 was profiled on peptide substrates and found to possess both trypsin-like and chymotrypsin-like activity. The ECM proteins lamanin and collagen-IV are thought to be substrates of Kallikrein 14. Endogenous inhibitors include kallistatin, protein-C inhibitor and alpha1-proteinase inhibitor, although Kallikrein 14 can be found complexed to a number of different proteinase inhibitors.