Cloning, Expression, Purification and Functional Study of Low-temperature Chitinase Pbchi5 Gene from Marinederived Photobacteria

Abstract

BACKGROUND: Chitin is the second largest carbon source on the earth, and chitosan oligosaccharides produced by its degradation have good application prospects in medicine, cosmetics, and agricultural production. OBJECTIVE: The discovery of a chitinase with high efficiency, high stability and clear degradation mechanism is of great help to promote the research of chitin derivatives and the development of the industrial chain. MATERIALS AND METHODS: In this experiment, a lowtemperature chitinase-producing strain Photobacterium sp. LG-29 was isolated from deep-sea mud in the Bohai Sea, and studied by means of molecular biology, biochemistry and bioinformatics. RESULTS: Purification of chitinase yielded an enzyme solution with a concentration of 0.918 mg/mL and a specific activity of 21.036 U/mg. The optimum action temperature is 35°C, and it is still active at 4°C, showing low-temperature enzymatic activity, and also has certain thermal stability. The optimum pH is 8.0, and it maintains more than 70% of the enzyme activity at pH 11, which is very stable in an alkaline environment. Mn2+, Ca2+, and Mg2+ are the main activators of enzymes, while Fe2+, Zn2+, etc. have extremely significant inhibitory effects on enzymes. The Km and Kcat of chitinase were determined to be 269.05 μ mol/L and 0.49 min-1, respectively. Chitinase PbCHI5 has both endonuclease and exonuclease activity. The theoretical pI of the enzyme is 4.16, which is a stable hydrophilic protein. CONCLUSION: This experiment laid a theoretical foundation for the development and utilization of new low-temperature chitinases.