Enzymatic determination of maltose by amperometric measurement of the rate of oxygen depletion

Abstract

An enzymatic method for the rapid, direct kinetic measurement of maltose is described. Maltose is hydrolysed to glucose by α-glucosidase, and the glucose reacts with oxygen in the presence of glucose oxidase to form gluconic acid and hydrogen peroxide. The rate of oxygen depletion is measured with a Clark oxygen electrode. The glucose oxidase reagent contains sufficient amounts of α-glucosidase impurity for a maximum reaction rate to be obtained within 2 min after addition of maltose to the reagent. The reaction rate is obtained directly by recording the derivative of the change in amperometric current. Glucose already present in samples can be destroyed by incubation with purified glucose oxidase reagent for 10 min. Fructose, lactose and galactose do not interfere. Interference from starch (constant over a wide range of starch concentrations) can be readily corrected for by adding starch to standards, and sucrose interference can be minimised by adjustment of the pH. Excellent results were obtained for the recovery of maltose from pooled serum samples.