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Ion-Specific Protein/Water Interface Determines the Hofmeister Effect on the Kinetic Stability of Glucose Oxidase
journal contribution
posted on 2019-09-11, 14:44 authored by Erik Sedlák, Dagmar Sedláková, Jozef Marek, Jozef Hančár, Katarína Garajová, Gabriel ŽoldákHomodimeric glucose
oxidase (GOX) from Aspergillus
niger is a prominent enzyme used for a number of applications
in biotechnology and clinical diagnostics. For robust and long-term
functional applications of GOX, the stability of the protein is of
utmost importance. In vitro, GOX is irreversibly inactivated over
time by a mechanism that is poorly understood, and hence, it presents
a significant drawback for the development of strategies to stabilize
the enzyme. We show that the nonequilibrium stability of GOX is fully
described by a one-step conformational unfolding kinetics. To explore
the strategies for improving GOX nonequilibrium stability, the effect
of salts of the Hofmeister series is examined using microcalorimetry.
We obtain activation energies Ea and inactivation
temperatures Tk (at which the irreversible
step is 1.0 min–1) as a function of the salt types
and concentrations. Based on the analysis by the extended Langmuir
model, we find that at high salt concentrations (>1 M) the Hofmeister
effect on inactivation temperature is determined by the universal
ion-specific effect on the protein/water interface, which apparently
does not depend significantly on a particular amino-acid sequence
and 3D protein structure. Our findings identify protein/water interfacial
tension as a critical physicochemical attribute of excipients that
is crucial for increasing enzyme kinetic stability.
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inactivation temperatures T kenzymeKinetic Stabilityion-specific effectsalt typesHofmeister seriesamino-acid sequenceinactivation temperatureGlucose Oxidase Homodimeric glucose oxidasestrategyGOX nonequilibrium stabilityHofmeister effectAspergillus niger3 D protein structureconcentrationactivation energies Eapplicationnonequilibrium stabilityHofmeister EffectLangmuir model
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