Periodic Acid Oxidation of Carbohydrates

Periodic acid oxidation (Section 15 12) finds extensive use as an analytical method m carbohydrate chemistry Structural information is obtained by measuring the number of equivalents of periodic acid that react with a given compound and by identifying the reaction products A vicinal diol consumes one equivalent of penodate and is cleaved to two carbonyl compounds... 

Hydrazide groups can react with carbonyl groups to form stable hydrazone linkages. Derivatives of proteins formed from the reaction of their carboxylate side chains with adipic acid dihydrazide (Chapter 4, Section 8.1) and the water-soluble carbodiimide EDC (Chapter 3, Section 1.1) create activated proteins that can covalently bind to formyl residues. Hydrazide-modified enzymes prepared in this manner can bind specifically to aldehyde groups formed by mild periodate oxidation of carbohydrates (Chapter 1, Section 4.4). These reagents can be used in assay systems to detect or measure glycoproteins in cells, tissue sections, or blots (Gershoni et al., 1985). 

Certain solubility factors are to be considered in work with periodate at different pH values. Above pH 5, disodium paraperiodate (Na2HJ06) tends to crystallize from aqueous solutions.246 Below pH 5, the sodium salt of periodic acid is more soluble, whereas above pH 5, the potassium salt is best employed. Phosphate-buffer solutions cause erroneous results,23 69a 60 61 and should be avoided in oxidations of carbohydrates. 

Measurement of the acidity produced in the periodate oxidation of carbohydrates is confined mainly to the determination of formic acid. Only from unsubstituted ketoses is the formation of such acids as glyoxylic and glycolic to be expected in carbohydrate chemistry.274... 

Bobbitt, J. M., Periodate Oxidation of Carbohydrates, 11, 1-41 BOeseken, j., Tbe Use of Boric Acid for the Determination of the Configuration of Carbohydrates, 4, 189-210 Bonner, T. G., Applications of Tri-fluoroacetic Anhydride in Carbohydrate Chemistry, 15, 59-84 Bonner, William A., Friedel-Crafts and Grignard Processes in the Carbohydrate Series, 5, 251-289 Bourne, E. J., and Peat, Stanley, The Methyl Ethers of D-Glucose, 5, 145-190... 

Horseradish peroxidase (HRP, EC 1.11.17) was obtained from Huka. The oxidation of carbohydrate moieties of enzyme with periodic acid (0.04 mM in 0.05 mM acetate buffer, pH 5.0) was performed according to Zaborsky and Ogletree (1974). The unreacted periodic acid was removed with 0.025-ethylene glycol. The oxidized enzymes were dialyzed against 50 mM phosphate buffer with pH 6.0 for 18 h. 

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