Component of the extracellular signaling pathway that establishes the dorsal-ventral pathway of the embryo. Three proteases; ndl, gd and snk process easter to create active easter. Active easter defines cell identities along the dorsal-ventral continuum by activating the spz ligand for the Tl receptor in the ventral region of the embryo. The clip domain consists of 35-55 residues which are 'knitted' together usually by 3 conserved disulfide bonds forming a clip-like compact structure. Belongs to the peptidase S1 family. CLIP subfamily.