Enkephalin-Degrading Aminopeptidase in the Longitudinal Muscle Layer of Guinea Pig Small Intestine: Its Properties and Action on Neuropeptides

• Published in: Journal of biochemistry (Tokyo) Vol. 109; no. 3; pp. 492 - 497
• Main Authors: Shimamura, Mariko, Hazato, Tadahiko, Iwaguchi, Takao
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.03.1991
• Subjects: aminopeptidase; Aminopeptidases - chemistry; Aminopeptidases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Anti-Bacterial Agents; Biological and medical sciences; CD13 Antigens; enkephalins; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Hydrolases; Hydrolysis; Hydroxamic Acids - pharmacology; Ileum - drug effects; Ileum - enzymology; Kidney - drug effects; Kidney - enzymology; Leucine - analogs & derivatives; Leucine - pharmacology; Molecular Weight; Muscles - drug effects; Muscles - enzymology; Neuropeptides - metabolism; Oligopeptides - pharmacology; Peptides; Substrate Specificity; Purification; Enzyme; Rodentia; Gut; Homology; Neuropeptide; Membrane enzyme; Vertebrata; Mammalia; Guinea pig; Enzymatic activity; Substrate specificity; Muscle; Physicochemical properties
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/oxfordjournals.jbchem.a123409

A membrane-bound enkephalin-degrading aminopeptidase was purified from the longitudinal muscle layer of the guinea pig small intestine by four steps of column chromatogra-phy using L-tyrosine β-naphthylamide. The molecular weight of the enzyme was estimated to be 106,000 by gel filtration. The maximum activity was observed between pH 6.5 and 7.0. The Km value for leucine-enkephalin was 137 μM. The aminopeptidase activity toward aminoacyl β-naphthylamide substrates was restricted to basic, neutral, and aromatic aminoacyl derivatives. No action was detected on acidic amino acid and proline derivatives. The enzyme was potently inhibited by the aminopeptidase inhibitors actinonin, amastatin, and bestatin, and bioactive peptides such as angiotensin III, substance P, and Met-Lys-bradykinin. The enzyme activity was also inhibited by the antibody against the purified serum enkephalin-degrading aminopeptidase of guinea pig at concentrations similar to those at which activity was observed toward serum enkephalin-degrading aminopeptidase and renal aminopeptidase M. The enzyme rapidly hydrolyzed Leu-enkephalin and Met-enkephalin with the sequential removal of the N-terminal amino acid residues. The enzyme also hydrolyzed two enkephalin derivatives, angiotensin III and neurokinin A. However, neurotensin, substance P, and bradykinin were not cleaved. These properties indicated that the membrane-bound enkephalin-degrading aminopeptidase in the longitudinal muscle layer of the small intestine is similar to the serum enkephalin-degrading aminopeptidase and resembles aminopeptidase M. It is therefore suggested to play an important role in the metabolism of some bioactive peptides including enkephalin in peripheral nervous systems in vivo.