Metalloendopeptidase which participates in the breakdown of the egg envelope at the time of hatching. Cleaves the N-terminal regions of the zona pellucia glycoproteins ZP2 and ZP3, where it specifically recognizes the peptide sequences TVQQS-|-DYLIK (major site) and KLMLK-|-APEPF (minor site). Hydrolysis of the inner layer of fish egg envelope. Also hydrolysis of casein and small molecule substrates such as succinyl-Leu-Leu-Val-Tyr-|-7-(4-methyl)coumarylamide. Binds 1 zinc ion per subunit. Expressed in cells of the hatching gland. Detected in embryos just before the bud stage, in an oval patch in the polster (anterior prechordal plate) (PubMed:9108332). At the 3-somite stage, found in a horseshoe-shaped cluster of cells surrounding the head primordium (PubMed:9108332). From 24 hours post-fertilization (hpf) onwards, expressed in a belt-like shape on the anterior surface of the yolk sac (PubMed:9108332, PubMed:19021768). Little or no expression detected after hatching (PubMed:9108332, PubMed:19021768).