Transglycosylation by a chitinase from Enterobacter cloacae subsp. cloacae generates longer chitin oligosaccharides

Abstract

Humans have exploited natural resources for a variety of applications. Chitin and its derivative chitin oligosaccharides (CHOS) have potential biomedical and agricultural applications. Availability of CHOS with the desired length has been a major limitation in the optimum use of such natural resources. Here, we report a single domain hyper-transglycosylating chitinase, which generates longer CHOS, from Enterobacter cloacae subsp. cloacae 13047 ( Ec Chi1). Ec Chi1 was optimally active at pH 5.0 and 40 °C with a K m of 15.2 mg ml −1 , and k cat /K m of 0.011× 10 2 mg −1 ml min −1 on colloidal chitin. The profile of the hydrolytic products, major product being chitobiose, released from CHOS indicated that Ec Chi1 was an endo-acting enzyme. Transglycosylation (TG) by Ec Chi1 on trimeric to hexameric CHOS resulted in the formation of longer CHOS for a prolonged duration. Ec Chi1 showed both chitobiase and TG activities, in addition to hydrolytic activity. The TG by Ec Chi1 was dependent, to some extent, on the length of the CHOS substrate and concentration of the enzyme. Homology modeling and docking with CHOS suggested that Ec Chi1 has a deep substrate-binding groove lined with aromatic amino acids, which is a characteristic feature of a processive enzyme.