Question

Von Gierke disease is frequently the result of a defect in glucose 6-phosphatase. Suggest another mutation in glycogen metabolism that could cause symptoms like those of von Gierke disease. Explain why the two mutants would likely share symptom profiles.

Answer 1

Introduction: Von Gierke disease is a type of glycogen storage diseases. It is a disorder where the stored glycogen cannot be converted to glucose due to the enzyme lack of enzyme glucose-6-phosphatase. Glycogen is the storage form of glucose which is needed by the body during an energy surge.

Explanation:

Glycogen storage disease is an inborn error of metabolism. Glycogen storage disease is of several types: type I to type VIII. Type I is the most commonly occuring disease. Von Gierke disease is a Type I glycogen storage disease. There are two sub - types of type I disorder: Type Ia and Type Ib.

· Type Ia known as Von Gierke disease occuring due to glucose-6-phosphatase deficiency.

· Type Ib which occurs due to glucose-6-phosphate transporter deficiency.

Both are autosomal recessive disorders. Both display similar symptoms of fatigue, hypoglycemia, lactic acidosis, hyperuricemia, growth retardation and hepatic adenomas. In addition the Type Ib also show symptoms of neutropenia and inflammatory bowel disease.

The glucose-6-phosphatase complex is a multi-subunit protein. It is referred to at the glucose-6-phosphatase system. The system is made of four separate proteins, which includes glucose-6-phosphatase-α catalytic subunit (G6PC), glucose-6-phosphate transporter (G6PT), glucose transporter and phosphate transporter. Both the glucose-6-phosphatase and glucose-6-phosphate transporter exists as a single copy gene and together maintain glucose homeostasis. Any mutation in the genes, alters the glucose – glycogen homeostasis. Hence, both mutants Ia and Ib share similar symptoms.