Allosteric transition and substrate binding are entropy-driven in glucosamine-6-phosphate deaminase from Escherichia coli.
Glucosamine-6P-deaminase (EC 3.5.99.6, formerly glucosamine-6-phosphate isomerase, EC 5.3.1.10) from Escherichia coli is an attractive experimental model for the study of allosteric transitions because it is both kinetically and structurally well-known, and follows rapid equilibrium random kinetics, so that the kinetic K(m) values are true thermodynamic equilibrium constants. The enzyme is a typical allosteric K-system activated by N-acetylglucosamine 6-P and displays an allosteric behavior that can be well described by the Monod-Wyman-Changeux model. This thermodynamic study based on the temperature dependence of allosteric parameters derived from this model shows that substrate binding and allosteric transition are both entropy-driven processes in E. coli GlcN6P deaminase. The analysis of this result in the light of the crystallographic structure of the enzyme implicates the active-site lid as the structural motif that could contribute significantly to this entropic component of the allosteric transition because of the remarkable change in its crystallographic B factors.
Bustos-Jaimes
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Laboratorio de Fisicoquímica y Diseño de Proteínas, Ciudad Universitaria, Mexico City D.F., 04510, Mexico. ismaelb@servidor.unam.mx
Calcagno
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D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000378:metabolism; D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000378:metabolism; D000494:Allosteric Regulation / Q000502:physiology; D001665:Binding Sites / Q000502:physiology; D019277:Entropy; D004926:Escherichia coli / Q000201:enzymology*; D008956:Models, Chemical; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000502:physiology; D013696:Temperature; D013816:Thermodynamics
C010004:N-acetylglucosamine 6-phosphate; C020582:glucosamine-6-phosphate isomerase; D019747:Aldose-Ketose Isomerases; D000117:Acetylglucosamine