Concurrent enzyme reactions and binding events for chitinases interacting with chitosan oligosaccharides monitored by high resolution mass spectrometry

▶ Formation of chitooligosaccharide-chitinase non-covalent complexes in the mass range of 55 kDa was dissected by high resolution mass spectrometry. ▶ Chemical composition of bound and free chitooligosaccharide species and their products in complex mixtures was determined by FT-ICR MS at 9.4 T. ▶ Wild-type chitinase B is shown to undergo with chitooligosaccharides four interaction/reaction pathways: (1) hydrolysis, (2) non-productive binding, (3) transglycosylation, and (4) lactone formation. ▶ Site-directed mutation D142N in chitinase B is shown to largely enhance the transglycosylation process. ▶ Site-directed mutagenesis E144Q in chitinase B on the binding specifity to chitooligosaccharides is changed and the enzymatic activity abolished.