The Chitopentaose Complex of a Mutant Hen Egg-White Lysozyme Displays No Distortion of the-1 Sugar Away from a C-4(1) Chair Conformation

Glycosidase inhibitors frequently reflect either the charge or the `flattened' shape of the oxocarbenium-ion like transition state. Much of the impetus for such inhibitory strategies derives from historical studies on ligand binding to hen egg white lysozyme (HEWL); not least those suggesting that product complexes of the enzyme showed distortion of the pyranosides in the -1 subsite. Ironically, while distortion is undoubtedly a defining feature of glycosidases, product complexes themselves are rarely distorted. Here we show that the chitopentaose product complex of a mutant E35Q HEWL, solved at 1.8 angstrom resolution, is bound with all sugars in C-4(1) conformation.