Question

The enzyme glucose oxidase isolated from the mold Penicillium notatum catalyzes the oxidation of β-D-glucose to D-glucono-δ-lactone. This enzyme is highly specific for the β anomer of glucose and does not affect the α anomer. In spite of this specificity, the reaction catalyzed by glucose oxidase is commonly used in a clinical assay for total blood glucose –that is, for solutions consisting of a mixture of β-D-glucose and α-D-glucose. What makes it possible for this test to measure total blood glucose?

What makes it possible for this test to measure total blood glucose?

• The α anomer of glucose easily converts to the β anomer.
• Both α-D-glucose and B-D-glucose have a free anomeric carbon
• Glucose interconverts between the glucopyranose and glucofuranose forms.
• The β anomer is present in a much higher concentration than the α anomer. 

 

Aside from increased sensitivity, what major advantage does glucose oxidase offer over Fehling's reagent for measuring blood glucose?

• Fehling's reagent can only detect the linear form of glucose.
• Fehling's test cannot be used in the lab to estimate the relative amount of glucose.
• Fehling's reagent is not specific to glucose, detecting other reducing sugars.
• Fehling's test cannot detect the presence of the β anomer.

Answer 1

Answer 1a) The α anomer of glucose easily converts to the β anomer.

Reason- There is a very high rate of mutarotation between α anomer and β anomer. it means that α and β anomers can be easily interconverted. when β anomer of glucose is consumed by the enzyme glucose oxidase, α anomer gets converted to β anomer. in this way, total blood glucose level can be measured by the enzyme glucose oxidase.

Answer 2c) Fehling's reagent is not specific to glucose, detecting other reducing sugars.

Reason- Fehling reagent can react with any reducing sugar, while enzyme glucose oxidase specifically reacts with the glucose molecules. that is why glucose oxidase provides another advantage over Fehling's reagent.