Thermal and chemical inactivation of phytase from rice bean (Vigna umbellata Thunb.)

Abstract

This study aimed to evaluate the results of the thermal (50 °C) and the chemical inactivation kinetics (urea 0.1 M) of the rice bean phytase along with spectral analysis at elevated temperature (80 °C, 1 h) and in the presence of urea (8 M, 1 h). Thermal inactivation of the phytase from rice bean (Vigna umbellata), exhibited a biphasic kinetic pattern with a distinct fast and a slow phase in the loss of the activity. Bovine serum albumin showed a little protection. The ultraviolet spectrum of the heat-inactivated phytase exhibited a higher absorbance at all wavelengths in comparison to the native enzyme. The emission maxima of the native and heat-inactivated phytase were at 330 and 340 nm, respectively in the fluorescence spectrum. The intensity in the heat-treated enzyme was lower in comparison to the native enzyme. A biphasic curve was also obtained in the chemical inactivation of the phytase. The fluorescence spectrum exhibited a lower emission intensity in comparison to the native enzyme. The emission maximum of the inactivated phytase was at 335 nm. The result indicates that in the presence of urea, more tertiary structure is retained in comparison to the heat-inactivated phytase.