title: Inhibition of triosephosphate isomerase by phosphoenolpyruvate in the feedback-regulation of glycolysis.
abstract: The inhibition of triosephosphate isomerase (TPI) in glycolysis by the pyruvate kinase (PK) substrate phosphoenolpyruvate (PEP) results in a newly discovered feedback loop that counters oxidative stress in cancer and actively respiring cells. The mechanism underlying this inhibition is illuminated by the co-crystal structure of TPI with bound PEP at 1.6 Å resolution, and by mutational studies guided by the crystallographic results. PEP is bound to the catalytic pocket of TPI and occludes substrate, which accounts for the observation that PEP competitively inhibits the interconversion of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Replacing an isoleucine residue located in the catalytic pocket of TPI with valine or threonine altered binding of substrates and PEP, reducing TPI activity in vitro and in vivo. Confirming a TPI-mediated activation of the pentose phosphate pathway (PPP), transgenic yeast cells expressing these TPI mutations accumulate greater levels of PPP intermediates and have altered stress resistance, mimicking the activation of the PK-TPI feedback loop. These results support a model in which glycolytic regulation requires direct catalytic inhibition of TPI by the pyruvate kinase substrate PEP, mediating a protective metabolic self-reconfiguration of central metabolism under conditions of oxidative stress.
authors.affiliation: Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK.
authors.forename: Nana-Maria
authors.initials: NM
authors.lastname: Grüning
authors.forename: Dijun
authors.initials: D
authors.lastname: Du
authors.forename: Markus A
authors.initials: MA
authors.lastname: Keller
authors.forename: Ben F
authors.initials: BF
authors.lastname: Luisi
authors.forename: Markus
authors.initials: M
authors.lastname: Ralser
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D055162:Biocatalysis; D018360:Crystallography, X-Ray; D005986:Glyceraldehyde 3-Phosphate / Q000737:chemistry / Q000378:metabolism; D006019:Glycolysis; D006801:Humans; D007700:Kinetics; D056004:Molecular Dynamics Simulation; D010728:Phosphoenolpyruvate / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D014305:Triose-Phosphate Isomerase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D005986:Glyceraldehyde 3-Phosphate; D010728:Phosphoenolpyruvate; D014305:Triose-Phosphate Isomerase
keywords: feedback loop; glycolysis; phosphoenolpyruvate; pyruvate kinase; triosephosphate isomerase