Osmolytic Effect of Sucrose on Thermal Denaturation of Pea Seedling Copper Amine Oxidase
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Protein stability is a subject of interest by many researchers. One of the common methods to increase the protein stability is using the osmolytes. Many studies and theories analyzed and explained osmolytic effect by equilibrium thermodynamic while most proteins undergo an irreversible denaturation. In current study we investigated the effect of sucrose as an osmolyte on the thermal denaturation of pea seedlings amine oxidase by the enzyme activity, fluorescence spectroscopy, circular dichroism, and differential scanning calorimetry. All experiments are in agreement that pea seedlings amine oxidase denaturation is controlled kinetically and its kinetic stability is increased in presence of sucrose. Differential scanning calorimetry experiments at different scanning rates showed that pea seedlings amine oxidase unfolding obeys two-state irreversible model. Fitting the differential scanning calorimetry data to two-state irreversible model showed that unfolding enthalpy and T *, temperature at which rate constant equals unit per minute, are increased while activation energy is not affected by increase in sucrose concentration. We concluded that osmolytes decrease the molecular oscillation of irreversible proteins which leads to decline in unfolding rate constant.
KeywordsPea seedlings amine oxidase Sucrose Differential scanning calorimetry Stability
Pea seedlings amine oxidase
Differential scanning calorimetry
The excess heat capacity
Temperature at which rate constant equals unit per minute
The supports from Ardabil University of Medical Sciences and Center of Excellence in Biothermodynamics (CEBiotherm) are gratefully acknowledged. This investigation was also supported financially by Iran National Science Foundation, Grant Number 87040071.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflicts of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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