Problem: A 14-month-old male presented to the emergency room. The patient's mother indicated that the child would have decreased consciousness especially during the night. This had become more noticeable after the child was weaned from breast milk. Mother notes that 20 minutes after feeding, the child would appear normal. The attending physician ordered a fasting test. Results showed marked hypoglycemia (39.8 mg/dl) and a -hydroxybutyrate level of 1.5 mM (normal = < 0.5 mM). These results indicated the child was suffering from hyperketotic hypoglycemia under fasting conditions. Under postprandial conditions, the patient was found to have hyperglycemia (up to 220 mg/dl) and hyperlactatemia (2.5 mM). A biopsy of skeletal muscle and liver were performed. The patient was found to have normal glycogen levels in skeletal muscle with severely reduced glycogen content in the liver. Both tissues had normal glycogen structure. There was no hepatomegaly noted. Blood uric acid levels were normal
From the list below, which enzyme is defective based on the patient symptoms and clinical findings? For each enzyme, provide a rationale for why it can or cannot be the defective enzyme in this patient based on the findings of the patient's medical workup. Each answer must include reference to the known function of the enzyme