Structure of human galactose mutarotase. Thoden J B et al. J. Biol. Chem. 2004;279:23431-23437 ©2004 by American Society for Biochemistry and Molecular Biology Structure of human galactose mutarotase. A ribbon representation of the three-dimensional architecture exhibited by the apoenzyme is shown in a. For clarity, only the major strands of the β-sheet are displayed. Asterisks indicate the positions of cis-Arg-78 and cis-Pro-103. The location of the active site is depicted in b as a space-filling representation. Note that the 3-, 4-, and 6-hydroxyl groups of galactose, from left to right and indicated by the red spheres, are solvent-exposed. The view is approximately the same as displayed in a.