title: Biochemical characterization of the mouse muscle-specific enolase: developmental changes in electrophoretic variants and selective binding to other proteins.
abstract: The glycolytic enzyme enolase (EC 4.2.1.11) is active as dimers formed from three subunits encoded by different genes. The embryonic alphaalpha isoform remains distributed in many adult cell types, whereas a transition towards betabeta and gammagamma isoforms occurs in striated muscle cells and neurons respectively. It is not understood why enolase exhibits tissue-specific isoforms with very close functional properties. We approached this problem by the purification of native betabeta-enolase from mouse hindlimb muscles and by raising specific antibodies of high titre against this protein. These reagents have been useful in revealing a heterogeneity of the beta-enolase subunit that changes with in vivo and in vitro maturation. A basic carboxypeptidase appears to be involved in generating an acidic beta-enolase variant, and may regulate plasminogen binding by this subunit. We show for the first time that pure betabeta-enolase binds with high affinity the adjacent enzymes in the glycolytic pathway (pyruvate kinase and phosphoglycerate mutase), favouring the hypothesis that these three enzymes form a functional glycolytic segment. betabeta-Enolase binds with high affinity sarcomeric troponin but not actin and tropomyosin. Some of these binding properties are shared by the alphaalpha-isoenolase, which is also expressed in striated muscle, but not by the neuron-specific gammagamma-enolase. These results support the idea that specific interactions with macromolecules will address muscle enolase isoforms at the subcellular site where ATP, produced through glycolysis, is most needed for contraction. Such a specific targeting could be modulated by post-translational modifications.
authors.affiliation: Biochimie Cellulaire, CNRS UPR 9065, Collège de France, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France.
authors.forename: T
authors.initials: T
authors.lastname: Merkulova
authors.forename: M
authors.initials: M
authors.lastname: Lucas
authors.forename: C
authors.initials: C
authors.lastname: Jabet
authors.forename: N
authors.initials: N
authors.lastname: Lamandé
authors.forename: J D
authors.initials: JD
authors.lastname: Rouzeau
authors.forename: F
authors.initials: F
authors.lastname: Gros
authors.forename: M
authors.initials: M
authors.lastname: Lazar
authors.forename: A
authors.initials: A
authors.lastname: Keller
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D009124:Muscle Proteins / Q000302:isolation & purification* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000196:embryology / Q000201:enzymology*; D010751:Phosphopyruvate Hydratase / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D010958:Plasminogen / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011817:Rabbits
chemical_list: D007527:Isoenzymes; D009124:Muscle Proteins; D010958:Plasminogen; D010751:Phosphopyruvate Hydratase