Serine protease with a variety of targets, including extracellular matrix proteins and proteoglycans such as biglycan, syndecan-4 and glypican-4. Through cleavage of proteoglycans, may release soluble FGF-glycosaminoglycan complexes that promote the range and intensity of FGF signals in the extracellular space. Consequently, facilitates inductive processes in the developing embryo, such as posteriorization, mesoderm induction and neuronal differentiation. Regulates the availability of insulin-like growth factors (IGFs) by cleaving IGF-binding proteins. Inhibits signaling mediated by TGF-beta family members. Consequently, may regulate many physiological processes. Intracellularly, degrades TSC2, leading to the activation of TSC2 downstream targets. Forms homotrimers. In the presence of substrate, may form higher-order multimers in a PDZ-independent manner. Predominantly secreted. Also found associated with the plasma membrane. First detected after midblastula transition. Expression increases during gastrulation and neurulation. Expressed in the blastopore lip at gastrula stage (stage 11), the posterior mesoderm and anterior neural plate after involution (stage 14), the early forebrain and midbrain-hindbrain boundary at the neurula stage (stage 16), and the branchial arch region in tail bud stage embryos (stage 26). Up-regulated by FGF4 and FGF8. Belongs to the peptidase S1C family. Truncated N-terminus.