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
Aldolase is an enzyme whose substrate is 
Select and explain. 
A. Glucose -6-phosphate, B. Fructose-6-phosphate, C. Fructose, D. Fructose-1 biphosphate
D: Fructose-1 biphosphate
Answer: D: Fructose-1 biphosphate 
Explanation: Ans. (d) Fructose-1, biphosphateRef: Harper's Biochemistry, 30 ed. pg. 202-203th* Aldolase B is preferentially expressed in the liver, while aldolase A is expressed in muscle and erythrocytes and aldolase C is expressed in the brain. Slight differences in isozyme structure result in different activities for the two substrate molecules: Fructose 1,6-Biphosphate and fructose 1-phosphate. Aldolase B exhibits no preference and thus catalyzes both reactions, while aldolases A and C prefer FBR* Aldolase A is an enzyme that catalyses a reversible aldol reaction: The substrate, fructose 1,6-bisphosphate (F- 1,6- BP) is broken down into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP).* Sucrose is composed of glucose and fructose and hence cannot be tolerated by patients of HFI.