Caractères et évolution des enzymes chitinolytiques chez les vertébrés inférieurs

The activity of chitinases extracted from various organs of different fish, amphibians and reptiles was estimated as a function of pH by using "native" chitin as substrate. Three types of chitinase activity were recorded, suggesting the existence of three different chitinase types : Type I : (optimum pH : 4.5, no activity at pH 1.0) was found in various organs, such as intestine, pyloric caeca, pancreas, liver, spleen, etc.) ; Type IIa : (optimum pH : 3.0, weak activity at pH 1.0) was obtained from the gastric mucosa of fish and one species of urodele ; Type IIb : (otimum pH : 3.0, strong activity at pH 1.0) was found in the gastric mucosa of reptiles and batrachian anura. Chitinase activity appears to be adapted to the pH of the digestive fluids. A tentative scheme is presented of chitinase evolution among lower vertebrates