Dear Hoda,

Since most chitinases are highly stable they possess some residual activity in the gel (SDS-PAGE) and therefore It is fairly simple. One sensitive substrate is 4MU conjugated to the NAGs with hope you know something about your enzyme specificity...

Take a look in Fig. 4 of the paper by Leonid Chernin (Molecular cloning, structural analysis, and expression in Escherichia coli of a chitinase gene from Enterobacter agglomerans. Appl. Environ. Microbiol. 1997, 63(3):834).

Good luck, Gali