Kinetic and Thermodynamic Parameters for Heat Denaturation of Cry1A(b) Protein from Transgenic Maize (Zea mays)

ABSTRACT:  The effect of heat treatment on the denaturation of Cry1A(b) protein expressed in transgenic maize was studied over a temperature range of 69 to 77 °C. Denaturation of Cry1A(b) protein was measured by the loss of reactivity with its specific antibodies using a sandwich ELISA. The process of denaturation was studied by analyzing the values of inmunoreactive protein after each heat treatment by kinetic analysis. Denaturation of Cry1A(b) protein was best described assuming a reaction order of 1.5. D -values calculated were 4338, 2350, 1272, 734, and 601 s at 69, 71, 73, 75, and 77 °C, respectively. Z -value was estimated to be 9.0 °C and the activation energy value was 266.15 kJ/mol. Thermodynamic parameters for the process of denaturation of Cry1A(b) protein were also calculated. The high values of the enthalpy of activation and the positive values of the entropy of activation obtained for Cry1A(b) protein are typical of a reaction in which the denaturation of the protein is the rate-determining process that predominates over an aggregation process during heating.