The present invention relates to a novel t-PALP protein which is a member of the serine protease family. In particular, isolated nucleic acid molecules are provided encoding the human t-PALP protein. t-PALP polypeptides are also provided as are vectors, host cells and recombinant methods for producing the same. The invention further relates to screening methods for identifying agonists and antagonists of t-PALP activity. Also provided are diagnostic methods for detecting circulatory system-related disorders and therapeutic methods for treating circulatory system-related disorders.