Blastula protease 10 (BP10), a metalloprotease of the astacin family, is secreted at the blastula stage by the sea urchin embryo. The BP10 gene shows a precise temporal and spatial regulation during embryogenesis. It has been cloned from a sea urchin lambda genomic library and the transcription unit has been entirely sequenced. It spans 6kb and contains seven exons (2.8 kb) and six introns (3.2 kb). Sequence comparison and phylogeny analysis show that BP10 belongs to a sub-family of molecular proteins which all play a role during development. In the two cases where the exon/intron organization of the gene is known (BP10 and tolloid), the modular structure of the protein is not reflected at the gene level, which indicates that this sub-family probably did not evolve by exon shuffling.