Answer to Question #171667 in Chemistry for ALISHBA PERVAIZ

Question

Blood glucose levels are measured by a procedure based upon the enzyme glucose oxidase. Since an enzyme is used, it is very specific for only D-glucose, and will not be subject to interferences from other molecules in the blood. Glucose is a reducing sugar, which means that it can be oxidized. How the tests for Blood Glucose (random and HbA1c) are conducted based on the reducing nature of monosaccharides?

Answer 1

Routine glucose test is based on the measuring of the solution colour which reflects the glucose concentration. More specifically, glucose oxidase catalyse the oxidation of D-glucose to D-glucono -1,5 - lactone with the production of hydrogen peroxide. Next, the lactone is hydrolysed to D-gluconic acid and the hydrogen peroxide is broken down to oxygen and water by a peroxidase enzyme. Oxygen reacts with an orthotoluidine which produces a coloured compound, the amount of which is measured colorimetrically. 

The HbA1c net FS test is also based on a colorimetric enzymatic method. The concentrations of HbA1c and total hemoglobin are determined separately. Fructosylated dipeptides from the N-terminal hemoglobin β-chain are released by a protease. Hydrogen peroxide is produced after oxidative cleavage of fructosylated dipeptides by fructosyl peptide oxidase and is determined colorimetrically by reaction with a chromogen in presence of peroxidase.