Search Organism: All OrganismsArabidopsis thalianaBacillus subtilis 168Bos taurusCaenorhabditis elegansCanis familiarisDanio rerioDrosophila melanogasterEquus caballusEscherichia coli K12Gallus gallusHomo sapiensMacaca mulattaMus musculusNematostella vectensisOryza sativaPan troglodytesRattus norvegicusSaccharomyces cerevisiaeSchizosaccharomyces pombeStrongylocentrotus purpuratusTakifugu rubripesXenopus laevis home support contribute downloads mirrors about us Eur. J. Endocrinol. Aug (1998); 139(2):224-30 Human leptin forms complexes with alpha 2-macroglobulin which are recognized by the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein. Birkenmeier G, Kampfer I, Kratzsch J, Schellenberger W Institute of Biochemistry, University of Leipzig, Germany. Abstract: OBJECTIVE: To identify binding proteins of leptin in human plasma. METHODS: Binding was evaluated by electrophoresis, size exclusion chromatography (SEC), Western blotting, and radioisotope labeling. Quantification of leptin and the different forms of alpha2-macroglobulin (alpha2-M) was performed by ELISA. RESULTS: Leptin interacts with the proteinase inhibitor, alpha2-M. 125I-labeled leptin specifically binds to the transformed inhibitor, which arises by reaction with proteinases or with reactive primary amines. No leptin binding was observed to the native alpha2-M, which abundantly occurs in plasma. The complex formation between leptin and alpha2-M was found to proceed within minutes and was stable, as it resisted separation by SEC and electrophoresis. The Kd of the complex was 2.14 +/- 0.78 micromol/l. Complex formation with transformed alpha2-M did not interfere with the immunological determination of leptin in plasma. The leptin-alpha2-M complex was found to be recognized by the alpha2-M receptor/low density lipoprotein receptor-related protein. By computer analysis, a simple model is presented showing that the degree of transformation of alpha2-M may significantly influence the leptin concentration in blood. CONCLUSIONS: The proteinase inhibitor, alpha2-M, may act as a leptin-binding protein in human plasma. Binding of leptin to transformed alpha2-M and its rapid clearance by the alpha2-M receptor may significantly influence the bioavailability of leptin in human plasma. [PUBMED: 9724081] Copyright © 2007, Tyers Lab, The Samuel Lunenfeld Research Institute, Mount Sinai Hospital, All Rights Reserved. terms and conditions - privacy policy - Osprey Network Visualization System BioGRID: A General Repository for Interaction Datasets. Chris Stark, Bobby-Joe Breitkreutz, Teresa Reguly, Lorrie Boucher, Ashton Breitkreutz, Mike Tyers. Nucleic Acids Res. Jan 1;34:D535-9.