Expression and enzymatic characterization of recombinant human kallikrein 14

Human kallikrein 14 (KLK14) is a member of the human kallikrein gene family of serine proteases, and its protein, hK14, has recently been suggested to serve as a new ovarian and breast cancer marker. To gain insights into hK14's physiological functions, the active recombinant enzyme was obtained in an enzymatically pure state for biochemical and enzymatic characterizations. We studied its substrate specificity and behavior to various protease inhibitors, and identified candidate physiological substrates. hK14 had trypsin-like activity with a strong preference for Arg over Lys in the P1 position, and its activity was inhibited by typical serine protease inhibitors. The protease degraded casein, fibronectin, gelatin, collagen type I, collagen type IV, fibrinogen, and high-molecular-weight kininogen. Furthermore, it rapidly hydrolyzed insulin-like growth factor binding protein-3 (IGFBP-3). These findings suggest that hK14 may be implicated in tumor progression in ovarian carcinoma.