A Structural Study by 19F-Nuclear-Magnetic Resonance of the Binding of Sugars to Lysozyme

1 The 19F chemical shifts of several fluorinated monosaccharide inhibitors have been determined in the inhibitor/lysozyme complexes. 2 The 19F shift of N-fluoroacetyl-α-D-glucosamine (αFAcGluNH2) in lysozyme is different from the β anomer and either α or β anomers of methyl N-fluoroacetyl-D-glucosamine (MeFAcGluNH2). 3 The 19F resonances of the inhibitors in the presence of lysozyme are broadened by addition of Gd(III) and the Gd(III)-F distances have been determined. 4 The distances for αFAcGluNH2 and αMeFAcGluNH2 are 0.56 nm while corresponding β values are 0.50 nm. Comparison with crystal models suggests a preferred orientation of the —CH2F groups. 5 Reference to a molecular model of lysozyme indicates that the 19F chemical shifts of the F3AcGluNH2· enzyme complexes arise from electrostatic effects of tryptophan-108 and tryptophan-63. 6 A combination of the Gd(III)-F distances and chemical shift data of the F3AcGluNH2· lysozyme complexes suggests that the co-ordinates of the —CF3 group are almost identical in the crystal phase and in solution.