Thermal stability studies of Vibrio cholerae L-asparaginase: Deactivation kinetics and stability enhancement
Remya Radha and Sathyanarayana N Gummadi
Indian Institute of Technology Madras, India
: J Food Nutr Disor
Abstract
Studies on deactivation kinetics as well as quantification of temperature dependent macromolecular properties of protein like activity and stability are ineluctable for predicting economic feasibility for industrial applications. L-asparaginase (L-asparagine amidohydrolase, E.C. 3.5.1.1) is an industrially important enzyme which catalyzes the conversion of L-asparagine to L-aspartate and ammonia. This enzyme has been using as a food processing enzyme as it can effectively reduce the level of acrylamide in a range of starchy foods. L-asparaginase also has application in the treatment of acute lymphoblastic leukemia and its clinical action is attributed to the depletion of L-asparagine, since tumor cells are impotent to synthesize this amino acid and are selectively killed by L-asparagine deprivation. This study reports the temperature dependent deactivation kinetics and stability studies of Vibrio cholerae L-asparaginase. Circular dichroism and differential scanning calorimetry studies have been carried out to understand the temperature-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase. Thermal stability studies on V. cholerae L-asparaginase revealed that the protein is stable up to 40 °C, retaining 70-85% residual activity even after 6 hours of incubation. Moreover it possessed very high melting point of 81 °C and high half-life time of 1100 minutes at 37 °C. Protein was found to be less stable at higher temperatures of 45, 50 and 55°C and residual activity was declined to 1-6 % in 15 minutes. The effect of various thermal additives like glycerol, glycine and trehalose on thermal stability of V. cholerae L-asparaginase was evaluated. Compared to other thermal stabilizers tested, glycine was found to be more effective which resulted in five folds increase in halflife time of enzyme at 50 °C.
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