Characterization of Chitotriosidase Enzyme Activity in the Serum of the American Alligator (Alligator mississippiensis)

Chitotriosidase (ChT) is an endoglucosaminidase enzyme that cleaves chitinous substrates and has been strongly associated with innate immune activity and the ability to identify non-selftissues. This enzyme activity was detected and characterized the serum from the American alligator (Alligator mississippiensis) using a fluorometric probe. Alligator serum exhibited volume-dependent activity, with activity (2.1 ± 0.3 μmol/min) observed at dilutions as low as a 1:150, and maximum activity (5.2 ± 0.6 μmol/min) measured at a dilution of 1:30. Alligator serum ChT showed linear activity for approximately 20 min, at which time activity decreased exponentially, presumably due to the depletion of substrate. In addition, the ChT activity in alligator serum was temperature-dependent with low activity at 5°C, a sharp increase from 10°C - 30°C, and maximal activity from 30°C - 40°C. The activity was inhibited in the presence of water-soluble chitin, but not mannan, indicating the specificity of the enzyme. The presence of ChT in alligator serum is likely to be partially responsible for the potent innate immune system of these crocodylians, and particularly antifungal activities.