Ion-Specific Protein/Water Interface Determines the Hofmeister Effect on the Kinetic Stability of Glucose Oxidase

Published on 2019-09-11T14:44:49Z (GMT) by
Homodimeric 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 <i>E</i><sub>a</sub> and inactivation temperatures <i>T</i><sub>k</sub> (at which the irreversible step is 1.0 min<sup>–1</sup>) 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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Sedlák, Erik; Sedláková, Dagmar; Marek, Jozef; Hančár, Jozef; Garajová, Katarína; Žoldák, Gabriel (2019): Ion-Specific Protein/Water Interface Determines the

Hofmeister Effect on the Kinetic Stability of Glucose Oxidase. ACS Publications. Collection.