title: Inversion of the allosteric response of Escherichia coli glucosamine-6-P deaminase to N-acetylglucosamine 6-P, by single amino acid replacements.
abstract: Amino acid replacements in the active site of glucosamine-6-P deaminase from Escherichia coli (GlcN6P deaminase, EC 3.5.99.6) involving the residues D141 and E148 produce atypical allosteric kinetics. These residues are located in the chain segment 139-156 which is part of the active site and which also forms several intersubunit contacts close to the allosteric site. In the D141N and E148Q mutant forms of this deaminase, there is an inversion of the effect of its physiological allosteric effector, N-acetylglucosamine 6-P, which becomes an inhibitor at substrate concentrations above a critical value. For both mutants, this particular point appears at low substrate concentration and the inhibition by the allosteric activator is the dominant effect in velocity versus substrate curves. These effects are analyzed as a particular case of the concerted allosteric model, assuming that the R state, the conformer displaying the higher affinity for the substrate, is the less catalytic state, thus producing an inverted allosteric response.
authors.affiliation: Laboratorio de Fisicoquímica e Ingeniería de Proteínas, Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), P.O. Box 70-159, Mexico City, D.F, 04510, Mexico.
authors.forename: David A
authors.initials: DA
authors.lastname: Cisneros
authors.forename: Gabriela M
authors.initials: GM
authors.lastname: Montero-Morán
authors.forename: Samuel
authors.initials: S
authors.lastname: Lara-González
authors.forename: Mario L
authors.initials: ML
authors.lastname: Calcagno
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000494:Allosteric Regulation; D000495:Allosteric Site; D019943:Amino Acid Substitution; D001665:Binding Sites; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D007527:Isoenzymes; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; C020582:glucosamine-6-phosphate isomerase; D019747:Aldose-Ketose Isomerases