Glycolysis

A 3-year-old boy from rural Maharashtra presents with recurrent episodes of severe hypoglycemia, lactic acidosis (pH 7.1, lactate 8 mmol/L), and hepatomegaly. His parents report that symptoms worsen during fasting and improve with frequent meals. Serum pyruvate is elevated at 4.2 mg/dL (normal <2). Blood glucose during a fasting challenge drops to 32 mg/dL within 4 hours. Liver biopsy shows glycogen accumulation. Which enzyme deficiency best explains this clinical presentation?

Which enzyme catalyzes the first committed step of glycolysis and is the primary site of allosteric regulation?