Publication Abstract from PubMed
Family 18 chitinases have the signature peptide DGXDXDXE forming the fourth beta-strand in the (beta/alpha)8-barrel of their catalytic domain. The carboxyl-end glutamic acid, E315 in Serratia marcescens chitinase A, serves as the acid/base during chitin hydrolysis, and the side-chain of the preceding aspartic acid, D313, helps to position correctly the N-acetyl moiety of the glycosyl sugar undergoing hydrolysis. Chitin substrates are bound within a long cleft across the top of the barrel, whose floor consists of aromatic residues that hydrophobically stack with every other GlcNAc. Alanine substitution of the conserved Trp167 at the -3 subsite in Serratia marcescens chitinase A enhanced transglycosylation. Higher oligosaccharides were formed from both chitin tetra- and pentasaccharide, and the only hydrolytic product from chitin trisaccharide was the disaccharide. Greater retention of the glycosyl fragment at the active site of the -3 mutant of Serratia marcescens chitinase A might favor transglycosylation due to a stabilized conformation of its D313.
Mutation of a conserved tryptophan in the chitin-binding cleft of Serratia marcescens chitinase A enhances transglycosylation.,Aronson NN Jr, Halloran BA, Alexeyev MF, Zhou XE, Wang Y, Meehan EJ, Chen L Biosci Biotechnol Biochem. 2006 Jan;70(1):243-51. PMID:16428843[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
