oxytocinase
{{Short description|Class of enzymes}}
Oxytocinase is a type of enzyme that metabolizes the endogenous neuropeptide, oxytocin.{{cite journal | vauthors = Tsujimoto M, Hattori A | title = The oxytocinase subfamily of M1 aminopeptidases | journal = Biochim. Biophys. Acta | volume = 1751 | issue = 1 | pages = 9–18 | year = 2005 | pmid = 16054015 | doi = 10.1016/j.bbapap.2004.09.011 }} The most well-characterized oxytocinase is leucyl/cystinyl aminopeptidase,{{cite journal | vauthors = Nomura S, Ito T, Yamamoto E, Sumigama S, Iwase A, Okada M, Shibata K, Ando H, Ino K, Kikkawa F, Mizutani S | title = Gene regulation and physiological function of placental leucine aminopeptidase/oxytocinase during pregnancy | journal = Biochim. Biophys. Acta | volume = 1751 | issue = 1 | pages = 19–25 | year = 2005 | pmid = 15894523 | doi = 10.1016/j.bbapap.2005.04.006 }} which is also an enkephalinase. Other oxytocinases are also known.{{cite journal | vauthors = Mizutani S, Yokosawa H, Tomoda Y | title = Degradation of oxytocin by the human placenta: effect of selective inhibitors | journal = Acta Endocrinol. | volume = 127 | issue = 1 | pages = 76–80 | year = 1992 | pmid = 1355623 | doi = 10.1530/acta.0.1270076}} During pregnancy, oxytocinase plays a role in balancing concentration of oxytocin by degrading the oxytocin produced by the fetus, as production of oxytocin increases with growth of fetus. One study found that concentration level of oxytocinase increased progressively with gestational age until labor, which indicates that pregnancy development can be statistically evaluated by comparing oxytocinase levels.{{Cite journal|last=Klimek|first=Marek|date=August 2005|title=Comparative analysis of ACTH and oxytocinase plasma concentration during pregnancy|journal=Neuro Endocrinology Letters|volume=26|issue=4|pages=337–341|issn=0172-780X|pmid=16136013}}
Inhibitors
Amastatin, bestatin (ubenimex), and puromycin have been found to inhibit the enzymatic degradation of oxytocin, though they also inhibit the degradation of various other peptides, such as vasopressin, met-enkephalin, and dynorphin A.{{cite journal | vauthors = Meisenberg G, Simmons WH | title = Amastatin potentiates the behavioral effects of vasopressin and oxytocin in mice | journal = Peptides | volume = 5 | issue = 3 | pages = 535–9 | year = 1984 | pmid = 6540873 | doi = 10.1016/0196-9781(84)90083-4| s2cid = 3881661 }}{{cite journal | vauthors = Stancampiano R, Melis MR, Argiolas A | title = Proteolytic conversion of oxytocin by brain synaptic membranes: role of aminopeptidases and endopeptidases | journal = Peptides | volume = 12 | issue = 5 | pages = 1119–25 | year = 1991 | pmid = 1800950 | doi = 10.1016/0196-9781(91)90068-z| s2cid = 36706540 }} EDTA, L-methionine, o-phenanthroline, and phosphoramidon have also been found to inhibit the enzymatic degradation of oxytocin.{{cite journal | vauthors = Itoh C, Watanabe M, Nagamatsu A, Soeda S, Kawarabayashi T, Shimeno H | title = Two molecular species of oxytocinase (L-cystine aminopeptidase) in human placenta: purification and characterization | journal = Biol. Pharm. Bull. | volume = 20 | issue = 1 | pages = 20–4 | year = 1997 | pmid = 9013800 | doi = 10.1248/bpb.20.20| doi-access = free }}