Inborn errors of metabolism are disorders resulting from genetic defects of meta
ID: 216364 • Letter: I
Question
Inborn errors of metabolism are disorders resulting from genetic defects of metabolic genes that regulate energy metabolism. Although rare, there 2 reported inborn errors of metabolism affecting the process of gluconeogenesis. The first results in a deficiency in fructose- 1,6 – bisphosphatase (FBPase) and the second results in a deficiency in phosphoenolpyruvate carboxylase (PEPCK). Both deficiencies present with the symptom of hypoglycemia (low blood glucose) early in life during periods of fasting. A. What are 3 main sources of glucose normally used to maintain euglycemia (normal blood glucose) in healthy individuals? B. Explain how deficiencies in either FBPase or PEPCK can lead to this symptom specifically during periods of fasting? Be sure to reference the sources listed in 1A. Please be brief. C. The hypoglycemia associated with PEPCK deficiency is often less frequent and less profound than in FBPase deficiency. Please explain this. (hint-think about the precursors for gluconeogenesis and how they are utilized within the gluconeogenic pathway). Please be brief. ?
Explanation / Answer
1. 3 main source of glucose in normal individual are
Through food
From glycogenolysis by liver by breaking down of glycogen to glucose
Through gluconeogenesis i.e glucose formation from other sources than glycogen
2. When person is on fasting then the process of gluconeogenesis starts to form glucose.
Fructose-16-bisphosphataseis an enzyme used in the process of gluconeogenesis to convert fructose 1,6 bisphosphate to fructose 6 phosphate. So its deficiency will stop gluconeogenesis and hence hypoglycemia occurs.
Also PEPCK used to convert oxaloactate to phosphoenol pyruvate which is used when gluconeogenesis uses protein,serine etc as subatrate.
3. PEPCK deficiency is an autosomal recessive disorder hence less frequent.
Second this enzyme comes in effect only when protein ,lactate and pyruvate are used to make glucose by gluconeogenesis which is very rare because the most common used substrates in gluconeogenesis are glycerol ,fructose,lysine ,serine hence the hypoglycemia due to its deficiency is very less profound.