Characterization of gastrointestinal chitinase in the lizard Sceloporus undulatus garmani (Reptilia : Phrynosomatidae)

Most studies on chitinase activity in lizards have been concerned with Pala earctic (European) and Laurasian (Middle Eastern and Asian) taxa. Several g enera of Old World lizards, Anguis, Uromastix, Chamaeleo and Lacerta, have been shown to possess chitinolytic activity. To date, only one New World li zard, Anolis carolinensis, has been reported to exhibit chitinolytic activi ty. In the present study, chitinase activity was characterized in a second New World taxon, Sceloporus undulatus garmani, a New World, phrynosomatid l izard. Chitinolytic activity was measured by incubating tissue extracts wit h a radioactive chitin substrate, acetyl-[H-3]chitin and determining acid s oluble radioactivity as an estimate for chitin hydrolysis. Chitinolytic act ivity was present in stomach, small intestine and pancreas extracts, with t he stomach and pancreas having the highest specific activities. Chitinolyti c activity was higher at pH 4.5 than at pH 7.5. The stomach chitinase is im munologically similar to the gastric chitinase previously described for rai nbow trout. Western blot analysis showed anti-chitinase cross-reactivity in the extracts of the stomach, but no cross-reactivity in the pancreatic or intestinal extracts, suggesting different isoforms of chitinase. There was no detected lysozyme activity (less than 0.01 mg/ml lysozyme) present in th e extracts of the stomach, small intestine and pancreas. The localization o f chitinolytic activity in S. u. garmani is in agreement with earlier repti lian reports on the distribution of chitinase. (C) 2001 Elsevier Science In c. All rights reserved.