Neurotensin‐Metabolizing Peptidases in Rat Fundus Plasma Membranes

AbstractThe mechanisms by which neurotensin (NT) was inactivated by rat fundus plasma membranes were characterized. Primary inactivating cleavages occurred at the Arg8‐Arg9, Pro10‐Tyr11, and Ile12‐Leu13 peptidyl bonds. Hydrolysis at the Arg8‐Arg9 bond was fully abolished by the use of N‐[1 (R,S)‐carboxy‐2‐phenylethyl]‐alanyl‐alanyl‐phenylalanine‐p‐aminobenzoate, a result indicating the involvement at this site of a recently purified soluble metallopeptidase. Hydrolysis of the Pro10‐Tyr11 bond was totally resistant to N‐benzyloxycarbonyl‐prolyl‐prolinal and thiorphan, an observation suggesting that the peptidase responsible for this cleavage was different from proline endopeptidase and endopeptidase 24.11 and might correspond to a NT‐degrading neutral metallopeptidase recently isolated from rat brain synaptic membranes. The enzyme acting at the Ile12‐Leu13 bond has not yet been identified. Secondary cleavages occurring on NT degradation products were mainly generated by bestatin‐sensitive aminopeptidases and post‐proline dipeptidyl aminopeptidase. The content in NT‐metabolizing peptidases present in rat fundus plasma membranes is compared with that previously established for purified rat brain synaptic membranes.

Neurotensin‐Metabolizing Peptidases in Rat Fundus Plasma Membranes Journal Articles