paper accepted: “The pattern of acetylation defines the priming activity of chitosan tetramers“

Today, Dr. Sven Basa’s paper on the role of the pattern of acetylation for the biological activity of chitosan oligomers was accepted for publication in the highly renowned Journal of the American Chemical Society - JACS. This paper has been really long in the making. Already 15 years ago, we had suspected that the pattern of acetylation may crucially define the bioactivities of chitosans, but we were unable to test this hypothesis because chitosans with defined patterns were not available. Finally now, we have proven it! Ten years ago, Talita Honorato, a Brazilian sandwich doctoral student in our group, found that the biological activities of chitosan oligomers depended on the chitinolytic enzyme used for its production. Our Indian doctoral candidate Malathi Nampally then found a bacterial chitosanase that produces priming-active oligomers from chitosan polymers, while a bacterial chitinase did not. Sven then identified the tetramers as the smallest priming active oligomers, characterized the differences between the tetramers produced using either enzyme, and identified the most active mono-acetylated tetramer. Our Indian sandwich doctoral student Subha Das from Prof. Appa Rao Podile’s group then proved that our observation was not limited to one special chitosanase but was reproducible with a different enzyme which had the same subsite specificities and, hence, produced the same oligomers. We now know that the mono-acetylated chitosan tetramer carrying its acetyl group at the non-reducing end unit has the highest priming activity; the other three isomers are much less active or inactive. The information for the bioactivity lies in the pattern of acetylation. We are sure that this is just a beginning. Deciphering the chitosan code. Nouri’s deepest scientific dream beginning to come true!