Carbohydrate binding at the active site of Escherichia coli maltodextrin phosphorylase

Abstract The oligosaccharide binding site of E. coli maltodextrin phosphorylase was characterised by a site-directed mutagenesis approach. Kinetic studies with oligosaccharides of different length imply that the oligosaccharide binding site consists of five subsites. Subsite five contributes about 14 kJ/mol to binding. Mutations of active site residues E67, E350 and H536 impair oligosaccharide binding significantly. Based on molecular modelling studies residues E350 and H536 appear to be important parts of subsite five, while residue E67 most likely contacts subsite two, which also seemed to be important for binding. Subsites three and four appeared to contribute only little to oligosaccharide binding energy.