Optimization of Chitin and Chitosan Modifying Enzymes for specific Chitosans

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Janina Hossbach, S Kolkenbrock, BM Moerschbacher

Department of Plant Biology and Biotechnology, Germany

Chitosan is one of the most versatile functional biopolymers, and it is commercially derived from the renewable resource chitin, one of the most abundant biopolymers on earth. It already has been shown that the degree of polymerization (DP) and the degree of acetylation (DA) are parameters influencing the physico-chemical properties and biological activities, but there is still a lack of detailed understanding of structure/function relationships of partially acetylated chitosans at the molecular level. We have hypothesized that for the biological activities also the pattern of acetylation (PA) plays a crucial role, especially in a target tissue after possessing by a sequence-specific chitosan hydrolase. As commercially available chitosans are produced chemically from fully acetylated chitin, they invariably carry random PA, while enzymes have the potential to create non-random patterns. The role of PA has not yet been studied, mostly due to a lack of analytical methods and to the non-availability of chitosans with non-random PA. We here describe how chitin and chitosan modifying enzymes, such as chitin deacetylases and chitosan hydrolases, can be used for analysis and synthesis of chitosans with non-random PA. These enzymes are often arranged in a modular fashion, like glycoside hydrolase or carbohydrate esterase modules as the catalytic domain either without or in combination with one or more different carbohydrate-binding modules. We want to investigate how these modules influence the enzymes’ properties and mode of action towards possible substrates. Moreover, a combination of various modules, generating chimeric enzymes could alter, e.g. the substrate specificity, processivity, and the resulting product. By using bio-engineered enzymes with novel qualities, the production of designer chitosans with known structures and defined functions becomes feasible, as a prerequisite for the development of reliable chitosan-based products, e.g. for plant disease protection or scar-free wound healing.