Peptide YY(3-36) (PYY(3-36)) is a gut hormone that acts on Y2 receptors to reduce appetite. Obese humans are sensitive to the anorectic effects of PYY(3-36) and display a blunted postprandial rise in PYY(3-36). Bariatric surgery results in increased circulating PYY-immunoreactivity, which appears to play a role in postoperative weight loss. The utility of PYY(3-36) as an antiobesity treatment is limited by its short circulating half-life. Insight into the mechanisms by which PYY(3-36) is degraded may aid design of long-acting PYY(3-36) analogues or enzyme inhibitor therapies. We aimed to investigate the role of metalloendopeptidases in PYY(3-36) degradation and determine whether modulation of these enzymes enhanced PYY(3-36) plasma levels and bioactivity in vivo. Degradation and resultant cleavage products of PYY(3-36) were characterized after incubation with neprilysin and meprin β and with a kidney brush border preparation in vitro. Specific metalloendopeptidase inhibitors were coadministered with PYY(3-36) to mice and subsequent PYY(3-36) plasma levels and bioactivity determined. Meprin β cleaves PYY(3-36) at multiple conserved acidic sites. Blocking the actions of meprin β prevents the degradative effect of kidney brush borders on PYY(3-36). In mice, pretreatment with actinonin significantly prolonged the anorectic effect of PYY(3-36) and maintained higher PYY(3-36) plasma levels than treatment with PYY(3-36) alone. These studies suggest that inhibiting the degradation of PYY(3-36) using specific inhibitor therapies and/or the design of analogues resistant to cleavage by meprins may be useful to antiobesity therapeutics.