| Type: | Domain | Name: | Peptidase S1A, nudel |
| Description: | Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes []. They include a wide range of peptidase activity, including exopeptidase, endopeptidase, oligopeptidase and omega-peptidase activity. Many families of serine protease have been identified, these being grouped into clans on the basis of structural similarity and other functional evidence []. Structures are known for members of the clans and the structures indicate that some appear to be totally unrelated, suggesting different evolutionary origins for the serine peptidases [].Not withstanding their different evolutionary origins, there are similarities in the reaction mechanisms of several peptidases. Chymotrypsin, subtilisin and carboxypeptidase C have a catalytic triad of serine, aspartate and histidine in common: serine acts as a nucleophile, aspartate as an electrophile, and histidine as a base []. The geometric orientations of the catalytic residues are similar between families, despite different protein folds []. The linear arrangements of the catalytic residues commonly reflect clan relationships. For example the catalytic triad in the chymotrypsin clan (PA) is ordered HDS, but is ordered DHS in the subtilisin clan (SB) and SDH in the carboxypeptidase clan (SC) [, ].This domain is found in serine endopeptidases belonging to MEROPS peptidase family S1A (clan PA). It is found in unusual mosaic proteins, which are encoded by the Drosophila nudel gene (see ). Nudel is involved in defining embryonic dorsoventral polarity. 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. Nudel, pipe and windbeutel together trigger the protease cascade within the extraembryonic perivitelline compartment which induces dorsoventral polarity of the Drosophila embryo []. | Short Name: | Peptidase_S1A_nudel |
