NMR analysis of enzyme-catalyzed and free-equilibrium mutarotation kinetics of monosaccharides.

We have exploited the saturation difference (SD) NMR technique to investigate the mutarotations of two sugars, l-fucose and d-ribose, at equilibrium. The KM and kcat values of Escherichia coli FucU-catalyzed mutarotation of l-fucose have been determined by this technique, and the values of KM for alpha- and beta-forms are shown to be the same. Similarly, the spontaneous mutarotation of d-ribose was investigated by using the same method, and it was found that d-ribose has an exceptionally high spontaneous alpha-to-beta conversion rate only between the furan forms.