A novel thermostable chitinolytic machinery of Streptomyces sp. F-3 consisting of chitinases with different action modes

Abstract

Background The biodegradation of chitin is an important part of the carbon and nitrogen cycles in nature. Speeding up the biotransformation of chitin substrates can not only reduce pollution, but also produce high value-added products. However, this process is strictly regulated by the catalytic efficiency of the chitinolytic machinery. Therefore, it is necessary to study the mode of action and compound mechanisms of different chitin-degrading enzymes in depth to improve the catalytic efficiency of the chitinolytic machinery. Results The thermophilic bacterium Streptomyces sp. F-3 showed comparatively high chitin degradation activities. To elucidate the mechanism underlying chitin hydrolysis, six chitin degradation-related enzymes were identified in the extracellular proteome of Streptomyces sp. F-3, including three chitinases ( Ss Chi18A, Ss Chi18B, and Ss Chi18C) from the GH18 family, one GH19 chitinase ( Ss Chi19A), one GH20 β- N -acetylhexosaminidase ( Ss GH20A), and one lytic polysaccharide monooxygenase ( Ss LPMO10A) from the AA10 family. All were upregulated by chitin. The heterologously expressed hydrolases could withstand temperatures up to 70 °C and were stable at pH values of 4 to 11. Biochemical analyses displayed that these chitin degradation-related enzymes had different functions and thus showed synergistic effects during chitin degradation. Furthermore, based on structural bioinformatics data, we speculated that the different action modes among the three GH18 chitinases may be caused by loop differences in their active site architectures. Among them, Ss Chi18A is probably processive and mainly acts on polysaccharides, while Ss Chi18B and Ss Chi18C are likely endo-non-processive and displayed higher activity on the degradation of chitin oligosaccharides. In addition, proteomic data and synergy experiments also indicated the importance of Ss LPMO10A, which could promote the activities of the hydrolases and increase the monosaccharide content in the reaction system, respectively. Conclusions In this article, the chitinolytic machinery of a thermophilic Streptomyces species was studied to explore the structural basis for the synergistic actions of chitinases from different GH18 subfamilies. The elucidation of the degradation mechanisms of these thermophilic chitinases will lay a theoretical foundation for the efficient industrialized transformation of natural chitin. Electronic supplementary material The online version of this article (10.1186/s13068-019-1472-1) contains supplementary material, which is available to authorized ...

Feeding on fungi: genomic and proteomic analysis of the enzymatic machinery of bacteria decomposing fungal biomass

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“…Chitin is the main structural component of cell wall of fungus and invertebrates exoskeletons like insects and crustaceans [4]. With advancement, it has been shown that chitin and its derivatives are of pharmaceutical and other industrial importance [5]. Because of its various applications, it has got immense attention in the field of pharmacology, agriculture and biotechnology [6].…”

Cloning, Purification, and Characterization of a Novel Metagenome-Sourced Microbial Chitinase with Dual Catalytic Domains

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