Thermal Stability of r-Amylase from Malted Jowar (Sorghum bicolor)

Siva Sai Kumar, R. and Sridevi Annapurna, Singh and Appu Rao, A. G. (2005) Thermal Stability of r-Amylase from Malted Jowar (Sorghum bicolor). Journal of Agricultural and Food Chemistry, 53. pp. 6883-6888.

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Abstract

<p align="justify">Malted cereals are rich sources of R-amylase, which catalyzes the random hydrolysis of internal R-(1-4)-glycosidic bonds of starch, leading to liquefaction. Amylases play a role in the predigestion of starch, leading to a reduction in the water absorption capacity of the cereal. Among the three cereal amylases (barley, ragi, and jowar), jowar amylase is found to be the most thermostable. The major amylase from malted jowar, a 47 kDa R-amylase, purified to homogeneity, is rich in ‚ structure (60%) like other cereal amylases. Tm, the midpoint of thermal inactivation, is found to be 69.6 (0.3 °C. Thermal inactivation is found to follow first-order kinetics at pH 4.8, the pH optimum of the enzyme. Activation energy, Ea, is found to be 45.3 ( 0.2 kcal mol-1. The activation enthalpy (¢ H*),entropy (¢ S*), and free energy change (¢ G*) are calculated to be 44.6 ( 0.2 kcal mol-1, 57.1 ( 0.3 cal mol-1 K-1, and 25.2 ( 0.2 kcal mol-1, respectively. The thermal stability of the enzyme in the presence of the commonly used food additives NaCl and sucrose has been studied. Tm is found to decrease to 66.3 ( 0.3, 58.1 ( 0.2, and 48.1 ( 0.5 °C, corresponding to the presence of 0.1, 0.5,and 1 M NaCl, respectively. Sucrose acts as a stabilizer; the Tm value is found to be 77.3 ( 0.3 °C compared to 69.6 ( 0.3 °C in the control.</p>

Item Type:	Article
Uncontrolled Keywords:	Sorghum bicolor r-amylase thermal stability starch degradation malted cereal
Subjects:	600 Technology > 08 Food technology > 21 Cereals 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
Divisions:	Protein Chemistry and Technology
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	02 Dec 2005
Last Modified:	01 Jul 2015 11:53
URI:	http://ir.cftri.res.in/id/eprint/235

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