| Vasoactive intestinal peptide ( VIP ) and pituitary adenylate cyclase activating peptide ( PACAP 27 , but not PACAP 38 ) degradation by the neutral endopeptidase EC 3 . 4 . 24 . 11 . ^^^ VIP ( vasoactive intestinal polypeptide ) and PACAP ( pituitary adenylate cyclase activating polypeptide ) , which are potent relaxing agents in the airways , were submitted to in vitro degradation by the neutral endopeptidase EC 3 . 4 . 24 . 11 ( NEP ) , one of the most active peptidase in the lung , to test their relative resistance to proteolysis . ^^^ Both VIP and PACAP ( 1 27 ) were cleaved by NEP , but PACAP ( 1 38 ) was not . ^^^ Thus , the degradation of VIP and PACAP ( 1 27 ) by the neutral endopeptidase 24 . 11 might produce a VIP 1 receptor selective active metabolite , provided that very high VIP or PACAP ( 1 27 ) concentrations are achieved in the receptor vicinity . . ^^^ |