Inhibition of a family 18 chitinase by chitooligosaccharides

Inhibition of family 18 chitinases is emerging as a target for pest and fungal control as well as asthma and inflammatory therapy. To this regard, it is desirable to have access to non-toxic inhibitors that are easy to produce, and have high specificity and efficiency. Chitooligosaccharides (CHOS) that are partially N-acetylated have the potential to fulfill these requirements. In this work, a high molecular weight chitosan with a degree of acetylation of 0.65 was enzymatically degraded by chitinase C, a family 18 endochitinase from Serratia marcescens, to a degree of scission (the fraction of cleaved glycosidic linkages) of 0.2. The resulting CHOS were purified with respect to degree of polymerization (DP). CHOS of DP 5, 6, and 8, respectively, were allowed to interact with another type of family 18 chitinase from S. marcescens, chitinase B, used as a model enzyme for a group of family 18 chitinases with deep active site grooves that includes human enzymes. Products obtained after 7 h were isolated and their structures were determined using mass spectrometry. The IC50-values of the resulting CHOS solutions for ChiB were in the lower micromolar range (15–18 μM).