kallikrein-related peptidase 11 (KLK11), also known as hippostasin, trypsin-like serine protease and PRSS20, is a member of human tissue kallikrein family. It is a subgroup of serine proteases with diverse physiological functions, which is implicated in carcinogenesis and some have potential as novel cancer and other disease biomarkers.The KLK11 gene is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19.Two alternatively spliced forms exist, resulting in 250 (isoform 1) and 282 (isoform 2) amino acid sequences,respectively. Isoform 1 is predominantly expressed in brain whereas isoform 2 is preferentially expressed in prostate. KLK11 is a novel marker for ovarian and prostate cancer carcinomas. Recombinant human KLK11, after being activated by thermolysin, is active against a thioester substrate. This activity can be inhibited by AEBSF dichloroisocoumarin, and aprotinin.