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Effect of additives on kinetic thermal stability of polygalacturonase II from Aspergillus carbonarius: mechanism of stabilization by sucrose.

Devi, N. A. and Rao, A. G. A. (1998) Effect of additives on kinetic thermal stability of polygalacturonase II from Aspergillus carbonarius: mechanism of stabilization by sucrose. Journal of Agricultural and Food Chemistry, 46 (9). pp. 3540-3545.

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Abstract

The thermal inactivation of polygalacturonase (PG II; Mw = 42 kDa; EC 3.2.1.15) from Aspergillus carbonarius at optimum pH of the enzyme activity followed first-order kinetics both in the presence and absence of additives. The enzyme was stable below its optimum pH. Sodium chloride enhanced thermal stability, the midpoint of thermal stability (Tm), shifted by 6C, and the half-life at Tm increased by 68-fold. Except for ethylene glycol, the other polyhydric alcohols enhanced thermal stability in a concn.-dependent manner; the stabilizing effect by polyhydric alcohols increased with increase in hydroxyl content of the polyol. Activation enthalpy increased in the presence of 1M sucrose and 1M NaCl from 77 to 116 kcal mol-1; activation entropy increased from 169 to 290 cal deg-1 mol-1. The net free energy change of stabilization in the presence of stabilizers was 3-4 kcal mol-1. Thermal inactivation of the enzyme involved conformational changes and unfolding of the enzyme molecule; the major secondary structural element, beta structure, decreased and the tryptophan residues were exposed to solvent. Stabilization of enzyme by sucrose was by preventing unfolding of the enzyme.

Item Type: Article
Uncontrolled Keywords: ASPERGILLUS-; GLYCOSIDASES-; PECTIC-ENZYMES; STABILITY-; SUCROSE-; THERMOPHYSICAL-PROPERTIES; ASPERGILLUS-CARBONARIUS; KINETICS-; POLYGALACTURONASES-; STABILIZATION-; THERMAL-STABILITY
Subjects: 600 Technology > 08 Food technology > 31 Food Additives
500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 16 Enzyme Chemistry
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 08 Aug 2008 09:58
Last Modified: 30 Jun 2015 12:50
URI: http://ir.cftri.com/id/eprint/7772

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