Kinetic and Thermo-Inactivation Thermodynamic Parameters of a Novel Isolated Serratia Marcescens B4A Chitinase

Background: Chitinase is one of the essential enzymes that have broad applications in industrial, agriculture, medical through biodegradation of chitin and hence are in demand. Chitinase-producing Serratia marcescens B4A was cultured in the medium containing chitin and then was purified through ammonium sulfate precipitation and DEAE ion-exchange chromatography. The purity of chitinase was determined by one and two- dimension sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results: Its optimum activity was at pH 7.0 and temperature 50 °C and was stable at 90 °C for 60 min and over a pH range from 5.0 to 8.0. The Km, Vmax, kcat, and kcat/Km values were 3.72 mg/ml, 0.19 U/ml, 134.75 min-1, and 36.17 mg.min-1.ml-1, respectively that showed a high affinity of chitinase to the substrate and exhibited excellent catalytic efficiency. Investigation of irreversible thermo-inactivation of chitinase at a range of 60 to 90 °C revealed a high value of ΔG# with the low value of ΔH# and a negative value of ΔS#. Conclusions: These characteristics of Serratia marcescens B4A chitinase showed high tolerance to thermal denaturation. Therefore, it may have a positive impact on industrial, antifungal applications, and biodegrade chitin waste. The present study is the first report on the thermodynamic and kinetic characterization of chitinase from Serratia marcescens B4A.