tokens: Database searches revealed a 50 - 63 % similarity and 34 - 42 % identity with several families of serine proteases , in particular the trypsin - like proteases , members of the glandular kallikrein family ( including prostate - specific antigen , nerve growth factor gamma , and epidermal growth factor - binding protein ) and the activators for the kringle family proteins ( including the human tissue plasminogen activator and human hepatocyte growth factor activator ) .