Paper accepted: Engineering of a chitin deacetylase to generate tailor-made chitosan polymers

Today, Martin Bonin’s second central paper resulting from his doctoral project with us has been published in the renowned journal PLOS Biology. Martin’s ambition during his doctoral project had been an in depth understanding of structure-activity relationships in chitin deacetylases. We are using these enzymes for the biotechnological production of chitosan oligomers and polymers with different, non-random patterns of acetylation. Today’s “second generation (2G)” chitosans are well-defined in terms of their degree of polymerisation and acetylation, but have random acetylation patterns. We consider our biotech chitosans to be the first “3G” chitosans, but the small number of chitin deacetylases with known regio-selectivity currently available severely limits access to the broad space of different acetylation patterns possible. As a basis for the targeted engineering of these enzymes to adjust their regio-selectivity, Martin performed an in depth bioinformatic and biochemical study of the chitin deacetylase from the plant endophytic fungus Pestalotiopsis spec., including the design and mass spectrometric screening of a site saturation mutagenesis library and molecular dynamics simulations of enzyme substrate interactions. His work was supported by two students, Antonia Irion and Anika Jürß, and by a collaboration with Dr. Sergi Pascual and Prof. Antoni Planas from Barcelona. Together, they succeeded in winning a much deeper understanding of the factors influencing regio-selectivity of chitin deacetylases, and in producing the first muteins with changed regio-selectivity. This work clearly makes PesCDA now the best studied chitin deacetylase ever! And the insights gained during the project have led to the writing of a review article on these enzymes which will be submitted shortly.