This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Carbohydrates, Subject name: Biochemistry
Sodium fluoride is a good in-vitro preservative of glucose in blood samples because it inhibits: 
Select and explain. 
A. Enolase, B. Hexokinase, C. Phosphofructokinase, D. Pyruvate dehydrogenase
A: Enolase
Answer: A: Enolase 
Explanation: Ans. (a) EnolaseRef: Harper's Biochemistry, 30 edn. pg. 170-171th* Enolase, also known as phosphopyruvate hydratase, is a metallo-enzyme responsible for the catalysis of the conversion of 2-phosphoglycerate to phosphoenol pyruvate, the ninth and penultimate step of glycolysis.* If the sample for blood glucose is kept for some time, the Red blood cells will start consuming the sugar available and hence the final report shall be lower than actual.* Sodium flouride shall inhibit enolase and ensure an accurate result.