Stereochemical course of the hydrolysis reaction catalyzed by chitinases Al and D from Bacillus circulans WL‐12

Abstract
Chitinases A1 and D were purified from the periplasmic proteins produced by Escherichia coli HB101 harbouring recombinant plasmids carrying respectively the chiA and chiD genes of Bacillus circulans WL‐12. HPLC analysis indicated that during the hydrolysis of chitotriose, both chitinases initially produce N‐acetylglucosamine and only one anomer of chitobiose. 1H NMR spectroscopy of the hydrolysis of chitotetraitol showed that this anomer corresponds to β‐chitobiose, demonstrating that chitinases Al and D act by a molecular mechanism that retains the anomeric configuration. This mechanism is similar to that of lysozymes although both chitinases belong to a family of proteins sharing no demonstrable amino acid sequence similarity with lysozymes.