GASPs are secreted proteins that contain WAP, Follistatin/Kazal, Ig-like, two Kunitz and NTR domains. GASP-1 functions as an inhibitory binding protein of some TGF-beta family proteins including GDF-8 and GDF-11. GASPs are predicted to be multivalent protease inhibitors, and GASP-2 has been shown to selectively inhibit trypsin. GASP-1 and -2 are differentially expressed during development and in the adult.