This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urea cycle, Subject name: Biochemistry
In all of the following enzyme deficiencies, hyperammonemia is a common feature, EXCEPT: 
Select and explain. 
A. Argininosuccinate synthetase, B. Carbamoyl Phosphate synthetase (CPS-I), C. Ornithine transcarbamoylase (OTC), D. Ornithine amino transferase
D: Ornithine amino transferase
Answer: D: Ornithine amino transferase 
Explanation: Excess ornithine from urea cycle is taken by enzyme OAT (Ornithine amino transferase) OAT deficiency leads to gyrate atrophy. In this deficiency, plasma, urine, spinal fluid and aqueous humour concentration of ornithine levels are 10-20 times higher than normal Hyperammonemia is absent because urea cycle is not disrupted in this deficiency Hyperammonemia occurs in enzyme deficiency of Urea cycle