This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nucleotides, Subject name: Biochemistry
Orotic aciduria is due to deficiency of- 
Select and explain. 
A. Decarboxylase, B. Isomerase, C. Tyrosinase, D. Homogentisate oxidase
A: Decarboxylase
Answer: A: Decarboxylase 
Explanation: Oroticaciduria is a rare, Autosomal recessive disorder. It is the most common metabolic error in Pyrimidine Synthesis. OP (Orotate Phospho Ribosyl Transferase) & Decarboxylase are bifunctional enzymes in pyrimidine synthesis. There are two types of Orotic acidurias: Type I : Both enzymes deficient i.e. OP(Orotate Phosphoribosyl Transferase) and OMP Decarboxylase(it is a bifunctional enzyme) Type II - Only one enzyme deficient (mostly OMP decarboxylase)