Metalloendoprotease which cleaves peptides such as tachykinin peptide TK-2 at the amino side of hydrophobic residues (PubMed:15554877, PubMed:17157960). Functions in female fertility, embryogenesis and memory formation (PubMed:24395329, PubMed:27629706). Required in females for normal patterns of egg laying, probably due to its function in sperm retention and preventing sperm displacement by rival ejaculates (PubMed:24395329). Also required for normal patterns of hatching due to its important role in early embryonic development (PubMed:24395329). Required in the dorsal paired medial neurons for the proper formation of middle-term memory (PubMed:27629706). Also required in the mushroom body neurons where it functions redundantly with neprilysins Nep3 and Nep4 in normal long-term memory formation (PubMed:27629706). Preferential cleavage of polypeptides between hydrophobic residues, particularly with Phe or Tyr at P1'. Binds 1 zinc ion per subunit. Optimum pH is 7-7.5 at 35 degrees Celsius. A secreted form exists that is probably produced by proteolytic cleavage (Probable). In embryos, adult Malpighian tubules and testes, detected in the soluble fraction but is not detected in the membrane fraction (PubMed:15554877, PubMed:17157960). Detected in the stellate cells in the main segment and the bar-shaped cells in the initial segment of male and female Malpighian tubules (at protein level) (PubMed:15554877). Expressed in the spermatheca (at protein level) (PubMed:24395329). Expressed in the somatic cyst cells of the testes, with increased expression at the tail end of elongating cysts (PubMed:15554877, PubMed:24395329). Expressed in the ovaries with strong expression in the posterior polar cells and in border cells of stage 8, 9, and 10 follicles (PubMed:24395329). In adults and third-instar larvae, expressed in the brain, ventral ganglion, and stellate cells (PubMed:24395329). Also expressed in the foregut and the imaginal disks (eye, antennal and leg) of third-instar larvae (PubMed:24395329). In stage 17 embryos, expressed in the tracheal system, foregut, hindgut and epidermis (PubMed:24395329). Also expressed in the stellate cell progenitors of the caudal visceral mesoderm in embryos (PubMed:17157960). N-glycosylated. The soluble form is probably produced by proteolytic cleavage. RNAi-mediated knockdown in females mated to wild-type males results in laying of fewer eggs due to impaired sperm retention and increased sperm displacement by rival ejaculates (PubMed:24395329). Females also show a reduced hatch rate and only 20% of their progeny reach the adult stage (PubMed:24395329). Unhatched eggs are fertilized but contain a clear polar body rosette instead of an embryo, suggesting that the eggs activate and complete meiosis but then embryogenesis is arrested (PubMed:24395329). Wild-type females mated to males that undergo RNAi-mediated knockdown, display a slight reduction in fertility but lay the same number of eggs and have the same hatch rate as those mated to wild-type males (PubMed:24395329). RNAi-mediated knockdown in the dorsal paired medial neurons impairs middle-term memory (MTM), but has no effect on long-term memory (LTM) formation, normal aversion learning and anesthesia-resistant memory (ARM) (PubMed:27629706). RNAi-mediated knockdown in all mushroom body neurons has no effect on learning, ARM and LTM (PubMed:27629706). However, simultaneous knockdown with Nep3 does impair LTM, and simultaneous knockdown with both Nep3 and Nep4 results in a further reduction in LTM formation (PubMed:27629706). Simultaneous knockdown with only Nep4 has no effect on LTM formation (PubMed:27629706). Belongs to the peptidase M13 family.