In situ characterization of nasal leucine enkephalin degrading aminopeptidase susceptibility of the nasal enzyme to boronic acids and phosphorus-containing peptide and amino acid isosteres

• Published in: International journal of pharmaceutics Vol. 117; no. 2; pp. 181 - 188
• Main Authors: Hussain, Munir A., Mersinger, Lawrence, Maurin, Michael B., Kettner, Charles
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 18.04.1995; Elsevier
• Subjects: Aminopeptidase; Biological and medical sciences; General pharmacology; Leucine-enkephalin; Leucine-enkephalin degrading aminopeptidase; Medical sciences; Nasal enzyme; Peptide; Pharmacokinetics. Pharmacogenetics. Drug-receptor interactions; Pharmacology. Drug treatments; Leucine-enkephalin degrading aminopeptidase; Aminopeptidase; Peptide; Nasal enzyme; Leucine-enkephalin; Peptides; Rat; Rodentia; Enzyme inhibitor; In vitro; Hydrolysis; Leucine enkephalin; In vivo; Vertebrata; Mammalia; Animal; Enzymatic digestion; Pharmacokinetics; Intranasally administration
• ISSN: 0378-5173; 1873-3476
• DOI: 10.1016/0378-5173(94)00328-3

The N-terminal Tyr-Gly bond of leucine-enkephalin is specifically hydrolyzed during exposure to the nasal mucosa. Kinetic properties in situ indicate that this activity is due to a single enzyme which has a K M app of 0.4 mM for leucine-enkephalin. Analysis of initial rates of hydrolysis from earlier inhibition studies using boroalanine, boroleucine, and borovaline indicated that these inhibitors bind the nasal enzyme with K m app values of 0.009–0.02 μM. In addition, we have evaluated borophenylalanine ( K app i = 0.004 μM) in this study. Similarly, H-PheΨP(O)(OH)CH 2Phe-OMe binds the nasal aminopeptidase with a K app i of 0.2 μM. Comparison of these K i values with those of cytosolic aminopeptidase and microsomal aminopeptidase derived from porcine kidney, indicates that the nasal enzyme closely resembles the microsomal enzyme in properties. Major distinctions between the enzymes are: (1) the greater dependence of the cytosolic enzyme on the nature of the amino acid residue in the primary site (2) a much greater preference of both the microsomal and nasal enzyme for HPheΨ[P(O)(OH)CH 2]Phe-OMe over H-PheΨ[P(O)(OH) 2].