Question

Question 3 [30]
Fructose is a naturally occurring carbohydrate. There are three inborn errors of
metabolism associated with fructose metabolism.

3.1.	Discuss the three inborn errors of fructose metabolism in detail, paying attention to the biochemistry of the disorder, clinical manifestations and possible treatment. Indicate, with the aid of references, the prevalence of these disorders among South Africans. South African obesity rates are among the highest in Africa. What role does
3.2.
3.3.

fructose metabolism play in obesity? Explain your answer with the aid of a flow
diagram. (10)

Answer 1

Fructose is also a main sugar played a vital role in the human diet. There are about three well known inborn errors as follows: (1) Benign fructosuria due to deficiency of fructoketose, (2) Hereditary fructose intolerance and (3) Fructose bisphosphatase deficiency.

Benign fructosuria: essential fructosuria is caused by a deficiency of the ezyme hepatic fructokinase due to incomplete fructose metabolism in the liver. This enzyme involved in the degradation of fructose to fructose -1-phosphate in the liver. This is usually asympotomatic and diagonosed by excess excretion through urine. Genetically, this inborn error is an autosomal recessive manner by mutation in the KHK gene. The actual incidence of fructosuria is 1:130,000 till date.

Hereditary fructose intolerance is caused by the deficiency of the enzyme aldolase B. This inborn error ended up in the buildup of toxic sugar (fructose or sucrose) in the liver. Biochemical changes of aldolase B enzymes activity, stability and oligomerisation.