Question

A 4-year-old child presents with easy fatigability. The mother also complains that the child has increased hunger between meals, which is relieved after food. Liver examination revealed no glycogen. The enzyme most likely deficient is?

• A. Glycogen phosphorylase
• B. Glycogen synthase
• C. Debranching enzyme
• D. Glucose 6 phosphatase

Answer 1

The Correct Option is B

A 4-year-old child presents with symptoms indicating an issue with glycogen metabolism. The key symptom of no glycogen present in the liver is critical to diagnosing the enzyme deficiency. Glycogen is a storage form of glucose, synthesized by the enzyme glycogen synthase. In the absence or deficiency of this enzyme, the liver cannot produce glycogen, despite the availability of glucose. This results in the inability to store glucose, explaining why the child has increased hunger and is easily fatigued, since glycogen serves as a primary energy reserve.

Analyzing the options:

• Glycogen phosphorylase: This enzyme breaks down glycogen into glucose-1-phosphate but does not contribute to glycogen synthesis. A deficiency would result in glycogen buildup, which contradicts the symptom of no glycogen in the liver.
• Glycogen synthase: This is the enzyme responsible for glycogen synthesis. Its deficiency leads to the inability to store glycogen, which aligns perfectly with the symptoms presented.
• Debranching enzyme: Involved in glycogenolysis (glycogen breakdown), its deficiency results in abnormal glycogen structure, not an absence of glycogen.
• Glucose 6 phosphatase: Deficient in conditions like Von Gierke's disease, leading to hypoglycemia and liver glycogen accumulation, not absence.

From the analysis above, the enzyme most likely deficient in this scenario is glycogen synthase, as its deficiency aligns with the absence of glycogen in the liver and the child’s symptoms.