Peptide YY3–36 (PYY3–36) is a gut hormone that acts on Y2 receptors to reduce appetite. Obese humans are sensitive to the anorectic effects of PYY3–36 and display a blunted postprandial rise in PYY3–36. Bariatric surgery results in increased circulating PYY-immunoreactivity, which appears to play a role in postoperative weight loss. The utility of PYY3–36 as an antiobesity treatment is limited by its short circulating half-life. Insight into the mechanisms by which PYY3–36 is degraded may aid design of long-acting PYY3–36 analogues or enzyme inhibitor therapies. We aimed to investigate the role of metalloendopeptidases in PYY3–36 degradation and determine whether modulation of these enzymes enhanced PYY3–36 plasma levels and bioactivity in vivo. Degradation and resultant cleavage products of PYY3–36 were characterized after incubation with neprilysin and meprin β and with a kidney brush border preparation in vitro. Specific metalloendopeptidase inhibitors were coadministered with PYY3–36 to mice and subsequent PYY3–36 plasma levels and bioactivity determined. Meprin β cleaves PYY3–36 at multiple conserved acidic sites. Blocking the actions of meprin β prevents the degradative effect of kidney brush borders on PYY3–36. In mice, pretreatment with actinonin significantly prolonged the anorectic effect of PYY3–36 and maintained higher PYY3–36 plasma levels than treatment with PYY3–36 alone. These studies suggest that inhibiting the degradation of PYY3–36 using specific inhibitor therapies and/or the design of analogues resistant to cleavage by meprins may be useful to antiobesity therapeutics.