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

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.

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#.

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.