Identification and characterization of human and mouse ovastacin: a novel metalloproteinase similar to hatching enzymes from arthropods, birds, amphibians, and fish.

We have cloned and characterized human and mouse ovary cDNAs encoding a new protein of the astacin family of metalloproteinases, called ovastacin because of its predominant expression in ovarian tissues. Human and mouse ovastacins exhibit the same domain organization as other astacins, including signal sequence, propeptide, and metalloproteinase domain. However, ovastacins show an additional C-terminal domain of about 150 amino acids with no similarity to other ancillary domains present in the equivalent region of most astacins. Northern blot analysis of human tissues and cell lines revealed that ovastacin is only detected at significant levels in leukemia and lymphoma cells of different origin. In addition, RT-PCR analysis demonstrated that ovastacin is expressed in human and mouse ovary, in unfertilized mouse oocytes, and in 1.5-day-postcoitum preimplantation embryos. Further studies showed that superovulation caused a dramatic increase in the expression of mouse ovastacin, indicating that the production of this enzyme is under hormonal regulation. Human ovastacin was expressed in Escherichia coli and the purified recombinant protein hydrolyzed synthetic substrates used for assaying metalloproteinases. These activities were abolished by inhibitors of metalloproteinases, but not by inhibitors of other classes of proteases. On the basis of these results, we suggest that ovastacin could play in mammals a physiological function similar to that performed by hatching proteases in evolutionary distant species from arthropods to fish.