Serine protease that cleaves beta-casein/CSN2 as well as several extracellular matrix (ECM) proteoglycans such as decorin/DCN, biglycan/BGN and fibronectin/FN1. Inhibits signaling mediated by TGF-beta family proteins possibly indirectly by degradation of these ECM proteoglycans (By similarity). May act as a tumor suppressor. Negatively regulates, in vitro, trophoblast invasion during placental development and may be involved in the development of the placenta in vivo. May also have a role in ovarian development, granulosa cell differentiation and luteinization (By similarity). Homotrimer (By similarity). Interacts with TGFB1; the interaction inhibits TGFB-mediated signaling. Interacts with BMP4; the interaction inhibits BMP4-mediated signaling. Interacts with TGFB2, GDF5 and MYH9 (By similarity). Secretion increased during decidualization of endometrial stromal cells. Expressed in the ovary, essentially in granulosa cells in a follicle-stage specific manner. Highest levels found in large luteinizing granulosa cells. In the developing ovary, high expression, especially of the longer isoform, at 12 days of age after birth. Expression restricted to the interstitial cells surrounding the follicles. Levels are further increased during ovarian maturation. Belongs to the peptidase S1C family.