Enzymic methods of carbohydrate analysis

Hydrolysing enzyme Glycosidic Trivial name Hydrolysis products 

Enzymic methods for the quantitation of monosaccharides are employed when a higher degree of specificity is required than can be achieved by the majority of the chemical methods. They often enable the quantitation of one stereoisomer in the presence of others and can often differentiate between the a and 0 anomeric forms. 

The oxidation of a-D-glucose occurs at less than 1% of the rate of oxidation of the /3 anomer. Because these two forms exist in solution in equilibrium in the proportion of 36% (a) and 64% (/3), mutarotation of the a to the /3 form must be allowed to reach equilibrium in the sample and standards for consistent 

The rate of oxidation of other monosaccharides (e.g. galactose, mannose, xylose, arabinose and fructose) by glucose oxidase has been shown to be negligible or zero but some derivatives of glucose do react slightly, e.g. 2-deoxy-D-glucose shows a reaction rate of less than 5% of that with /3-D-glucose. 

Quantitation of glucose using glucose oxidase is achieved by measurement of either the hydrogen peroxide formed or the oxygen consumed during the reaction, both of which are proportional to the 3-D-glucose content of the sample. 

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