title: Identification of cytosolic leucyl aminopeptidase (EC 3.4.11.1) as the major cysteinylglycine-hydrolysing activity in rat liver.
abstract: Cysteinylglycine hydrolysis is a step in the metabolism of glutathione and glutathione S-conjugates. We had previously observed that in rat liver the enzymatic activity is predominantly located in the cytosol. Here we demonstrate that cytosolic leucyl aminopeptidase (EC 3.4.11.1) is the major cysteinylglycine hydrolysing activity in rat liver. Evidence was obtained from the use of peptidase inhibitors and from immunoprecipitation studies using Pansorbin-coupled antibodies raised against hog kidney cytosolic leucyl aminopeptidase. Both isolated cytosolic leucyl aminopeptidase and the cysteinylglycine-hydrolysing activity in rat liver cytosol are bound with equal efficiency to the affinity matrix. We demonstrate that cytosolic leucyl aminopeptidase exhibits leucinamidase and cysteinylglycinase activity. Cysteinylglycine, cystinyl-bis-glycine, S-nitrosocysteinylglycine, and bimane-S-cysteinylglycine are hydrolysed at high rates; low activity is seen with leukotriene D4. Our findings establish a previously unrecognised physiological function of cytosolic leucyl aminopeptidase, participating in glutathione metabolism and in the degradation of glutathione S-conjugates via the mercapturic acid pathway.
authors.affiliation: Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, D-40001 Düsseldorf, Germany.
authors.forename: Claudio
authors.initials: C
authors.lastname: Jösch
authors.forename: Lars-Oliver
authors.initials: LO
authors.lastname: Klotz
authors.forename: Helmut
authors.initials: H
authors.lastname: Sies
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000276:immunology; D003600:Cytosol / Q000201:enzymology; D004151:Dipeptides / Q000378:metabolism*; D006868:Hydrolysis; D007930:Leucine / Q000031:analogs & derivatives* / Q000378:metabolism; D007931:Leucyl Aminopeptidase / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D011233:Precipitin Tests / Q000379:methods; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D013379:Substrate Specificity; D013552:Swine
chemical_list: D000906:Antibodies; D004151:Dipeptides; D011480:Protease Inhibitors; C028505:cysteinylglycine; D007931:Leucyl Aminopeptidase; D007930:Leucine; C013086:leucinamide; D000111:Acetylcysteine