Biochemistry of fish stomach chitinase

Fish are reported to exhibit chitinase activity in the stomach. Analyses of fish stomach chitinases have shown that these enzymes have the physiological function of degrading chitinous substances ingested as diets. Osteichthyes, a group that includes most of the fishes, have several chitinases in their stomachs. From a phylogenetic analysis of the chitinases of vertebrates, these particular molecules were classified into a fish-specific group and have different substrate specificities, suggesting that they can degrade ingested chitinous substances efficiently. On the other hand, it has been suggested that coelacanth (Sarcopterygii) and shark (Chondrichthyes) have a single chitinase enzyme in their stomachs, which shows multiple functions. This review focuses on recent research on the biochemistry of fish stomach chitinases.