Human Kallikrein 11 (KLK11) is a member of tissue kallikrein family which are extracellular serine proteases consisting of 15 members. Two isoforms of KLK11 are differentially expressed. Isoform 1 is predominantly expressed in brain and isoform 2 is preferentially expressed in prostate. Isoform 1 consists of a signal peptide,a short pro peptide and the mature chain.Isoform 2 contains an extra 32 amino acid N terminal to full-length isoform 1.KLK11 is a novel marker for ovarian and prostate cancer carcinomas. KLK11 can be activated by thermolysin and is active against a thioester substrate.