Effects of three peptidase inhibitors, amastatin, captopril and phosphoramidon, on the hydrolysis of [Met5]-enkephalin-Arg6-Phe7 and other opioid peptides

Naunyn Schmiedebergs Arch Pharmacol. 1998 Mar;357(3):276-82. doi: 10.1007/pl00005168.


The contents of [Met5]-enkephalin-Arg6-Phe7 (met-enk-RF) and its six hydrolysis products: Y, YG, YGG, YGGF, YGGFM, and YGGFMR were estimated after incubating met-enk-RF with either a guinea-pig ileal or striatal membrane fraction for various times at 37 degrees C. After 45 min incubation with either ileal or striatal membranes, met-enk-RF was completely hydrolyzed, yielding Y as the major product. Incubation with either membrane preparation for 60 min in the presence of the aminopeptidase inhibitor amastatin hydrolyzed 90 or 92% of met-enk-RF, respectively, with YGG being the major product. If the dipeptidyl carboxypeptidase I inhibitor captopril is also included in the incubation, met-enk-RF hydrolysis decreases by about half for both membranes, with YGG remaining the major product. Inclusion of three peptidase inhibitors, amastatin, captopril, and phosphoramidon (inhibition of endopeptidase-24.11) further reduced met-enk-hydrolysis, with 87% or more remaining intact. This shows that met-enk-RF was mainly hydrolyzed by three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I and phosphoramidon-sensitive endopeptidase-24.11, in both ileal and striatal membranes. Additionally, estimations of [Leu5]-enkephalin (leu-enk), alpha- and beta-neoendorphins (alpha- and beta-neoends), and dynorphin B (dyn B) contents after incubating the individual peptides with striatal membrane for 60 min in the presence of the three peptidase inhibitors showed that 98, 32, 5, and 23%, respectively, remained intact. Our previous studies together with the data obtained here show that one group of endogenous opioid peptides: met-enk, leu-enk, met-enk-RF, met-enk-RGL, and dyn A-(1-8) are largely or almost exclusively hydrolyzed by the three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I, and phosphoramidon-sensitive endopeptidase-24.11, and indicate that an unidentified fourth enzyme(s) is involved in the hydrolysis of another group of peptides: alpha-neoend, beta-neoend, and dyn B.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin-Converting Enzyme Inhibitors / pharmacology*
  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Captopril / pharmacology*
  • Enkephalins / drug effects*
  • Enkephalins / metabolism
  • Glycopeptides / pharmacology*
  • Guinea Pigs
  • Hydrolysis / drug effects
  • Ileum / drug effects
  • Ileum / metabolism
  • Male
  • Membranes / drug effects
  • Membranes / metabolism
  • Opioid Peptides / drug effects*
  • Opioid Peptides / metabolism
  • Peptides*
  • Protease Inhibitors / pharmacology*
  • Visual Cortex / drug effects
  • Visual Cortex / metabolism


  • Angiotensin-Converting Enzyme Inhibitors
  • Anti-Bacterial Agents
  • Enkephalins
  • Glycopeptides
  • Opioid Peptides
  • Peptides
  • Protease Inhibitors
  • amastatin
  • Captopril
  • phosphoramidon