Proteolytic processing of a sea urchin, ECM-localized protein into lower mol mass species possessing...

The hyaline layer is an apically located extraembryonic matrix, which blankets the sea urchin embryo. Using gelatin substrate gel zymography, we have identified a number of gelatin-cleaving activities within the hyaline layer and defined a precursor-product processing pathway which leads to the appearance of 40- and 38-kDa activities coincident with the loss of a 50-kDa species. Proteolytic processing of the precursor required the presence of both CaCl2 and NaCl at concentrations similar to those found in sea water. The cleavage activities utilized both sea urchin and rat tail tendon gelatins as substrates but demonstrated a species-specific cleavage activity towards sea urchin collagen. The gelatin-cleaving activities were refractory to inhibition by 1,10-phenanthroline but were inhibited by benzamidine. This latter result defines the serine protease nature of the cleavage activities. Both the 40- and 38-kDa activities were found to comigrate with gelatin-cleaving activities present in the sea urchin embryo.