Characterization of a Chitinase Activity in the Gut of the Yellow‐Bellied Slider Turtle Trachemys scripta

The Slider Turtle, Trachemys scripta, undergoes an ontogenetic dietary shift from a largely insect based diet to a plant based diet. Throughout the shift, the turtles must be able to access and utilize the maximum nutritional content available in both diets. Digestive enzymes such as endochitinase and exochitinase have been found throughout the gut that assist in nutrient breakdown. This work aimed to isolate and characterize the enzyme chitinase found to be optimally active at pH values 2.5 and 5.0 in T. scripta. The two activities suggest the presence of a cofactor, differing mechanisms, or two separate enzymes at work. Exochitinase activity was assayed using an N‐acetyl‐β‐D‐glucosaminide substrate esterified with fluorescent 4‐methylumbelliferone, which yielded a fluorescent product upon cleavage by the enzyme. Salt precipitation with 90% saturated (NH 4 ) 2 SO 4 and ion exchange chromatography were two techniques used to attempt to isolate activity at either pH 5.0 or pH 2.5. Enzyme activity at pH 5.0 was precipitated using the 90% (NH 4 ) 2 SO 4 solution but at pH 2.5 only half of the original enzymatic activity was recovered. This work was sponsored by the Student Research Fund of Otterbein University.