A mechanistic study of sialic acid mutarotation: Implications for mutarotase enzymes

作者：Chan Jefferson; Sandhu Gurtej; Bennet Andrew J^*

来源：Organic and Biomolecular Chemistry, 2011, 9(13): 4818-4822.

DOI：10.1039/c1ob05079f

The mutarotation of N-acetylneuraminic acid (Neu5Ac) proceeds by four kinetically distinct pathways: (i) the acid-catalyzed reaction of neutral Neu5Ac; (ii) the spontaneous reaction of the carboxylic acid (the kinetically equivalent acid-catalyzed reaction on the anion being ruled out by the solvent deuterium kinetic isotope effect of 3.74 +/- 0.68); (iii) a spontaneous, water-catalyzed, reaction of the anion; and (iv) a specific-base catalyzed reaction of the anion. The magnitude of the solvent kinetic isotope effect, k(H2O)/k(D2O) = 4.48 +/- 0.74 is consistent with a ring-opening transition state in which a water molecule is deprotonating the anomeric hydroxyl group in concert with strengthening solvation of the ring oxygen atom. The mechanistic implications for Neu5Ac mutarotases are discussed.

• 出版日期2011