Kallikreins are a subgroup of serine proteases having diverse physiological functions. Growing evidence suggests that many kallikreins are implicated in carcinogenesis and some have potential as novel cancer and other disease biomarkers. KLK13 is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19. Expression of this gene is regulated by steroid hormones and may be useful as a marker for breast cancer. An additional transcript variant has been identified, but its full length sequence has not been determined. Recombinant human KLK13 protein, fused to His-tag at N-terminus, was expressed in E.coli.