A patient was born by Cesarean section at 36 weeks gestation with normal Apgars and birth weight. She was the sixth child of unrelated parents, and her siblings were all unaffected. She presented within 24 hours of life with Kussmaul breathing ( hyperventilation associated with the lung's emergency response to acidosis ) and severe metabolic acidosis ( lactic acidosis determined to be 15 mM ) , Lactic acid decreased site lasting and increased with carbohydrate feeding. During the first months, she had normal tone, reflexes, was fixing and following with her eyes, and did not have organomegaly. She was tachycardic 160 to 180 minute, a symptom that always persisted. The acidosis was treated with bicarbonate then oral citrate, and by carbohydrate restriction. Genotypic mutation andysis was performed. Of the following enzymes, which is the mont likely to be found mutated ( non - functional ) in the patient?

A lactate dehydrogenase
B. glucose 6 - phosphate dehydrogenase
C. pyruvate kinase
D. pyruvate carboxylase
E . succinyl - CoA synthetase