title: Zinc binding and its trapping by allosteric transition in glucosamine-6-phosphate deaminase from Escherichia coli.
abstract: Glucosamine-6-phosphate isomerase deaminase from Escherichia coli, a typical allosteric enzyme, becomes less cooperative and 50% inhibited when treated with zinc. This metal cation behaving as a tight-bound and slow partial inhibitor. Modification of a pair of vicinal reactive thiols with some sulfhydryl reagents mimics this effect. On the other hand, sulfhydryl reactivity disappears in the presence of saturating concentrations of Zn2+, which does not modify the kinetics of S-methylated enzyme, a finding that indicates that vicinal thiols are an essential part of the zinc-binding site. Allosteric activation of the deaminase causes trapping of the metal, which cannot be released by dialysis against a buffer containing EDTA. Cadmium and nickel(II) cations also produce a similar effect.
authors.affiliation: Departamento de Bioquimica, Facultad de Medicina, Universidad Nacional Autóma de Mèxico, Mexico City.
authors.forename: M M
authors.initials: MM
authors.lastname: Altamirano
authors.forename: M
authors.initials: M
authors.lastname: Calcagno
mesh_terms: D019747:Aldose-Ketose Isomerases; D000494:Allosteric Regulation; D001665:Binding Sites; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D008024:Ligands; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D015032:Zinc / Q000378:metabolism*
chemical_list: D008024:Ligands; D013438:Sulfhydryl Compounds; D004492:Edetic Acid; C020582:glucosamine-6-phosphate isomerase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; D015032:Zinc