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
Fructose intolerance is due to deficiency of: 
Select and explain. 
A. Fructokinase, B. Aldolase-B, C. Fructose 1,6 bisphosphatase, D. Fructose synthase
B: Aldolase-B
Answer: B: Aldolase-B 
Explanation: Ans: b (Aldolase - B) Ref: Vasudevan, 4th ed, p. 120Hereditary fructose intolerance is due to defect in the enzyme Aldolase-B.Hereditary fructose intolerance:Defect: Aldolase-B enzyme deficiency( fructose 1 PO4 aldolase activity).Lethargy, vomiting, diarrhoea, hypoglycaemia.Liver damage, hyper bilirubinaemia (deposition of fructose 1 PO4 in liver and kidney).Hyper uricaemia, lactic acidosis.Renal proximal tubular defect (fanconi).Cataract is not a feature of this disease, because fructose is not an Aldose sugar and therefore not a substrate for aldose reductase in the lens.Treatment - Eliminate fructose from diet.Fructokinase deficiency is usually asymptomatic.