Fig. 7

The proposed pathway of chitin degradation by the ChiUL. ChiA is fully secreted from the cell and hydrolyzes chitin by the combined actions of the N- and C-terminal GH18 domains and the carbohydrate-binding properties of ChiA_M. ChiB, while not as efficient as ChiA, hydrolyzes chitin and chitooligosaccharides (ChiOs) at the cell surface. The dual CusC/D pairs capture and import ChiOs into the periplasm, where the GH20 enzyme fully degrades them into monosaccharides. After import into the cytoplasm, NagK (Fjoh_4589), NagA (Fjoh_3974), and NagB are predicted to convert N-acetyl-glucosamine to fructose-6-phosphate