A HIGH-AFFINITY, MU-OPIOID RECEPTOR-SELECTIVE ENKEPHALIN ANALOG LACKING AN N-TERMINAL TYROSINE

We report a high affinity, mu opioid receptor selective enkephalin ana logue in which the N-terminal tyrosine residue thought to be required for such high affinity is replaced by phenylalanine. The high affinity can be traced to a shift of the ligand's N-terminal residue within th e mu receptor binding pocket, which diminishes the importance of the u sual hydrogen bond between the tyrosine phenolic moiety and the recept or. (C) 1998 Elsevier Science Ltd. All rights reserved.