maspin,peptidase inhibitor 5,PI5,PI-5,protease inhibitor 5 (maspin),serine (or cysteine) proteinase inhibitor, clade B (ovalbumin), member 5,serpin B5,serpin peptidase inhibitor, clade B (ovalbumin), member 5.
Tumor suppressor. It blocks the growth, invasion, and metastatic properties of mammary tumors. As it does not undergo the S (stressed) to R (relaxed) conformational transition characteristic of active serpins, it exhibits no serine protease inhibitory activity.