This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Amino acid which contributes to biosynthesis of purine ribonucleotide are all EXCEPT: 
Select and explain. 
A. Aspartate, B. Histidine, C. Glutamate, D. Glycine
B: Histidine
Answer: B: Histidine 
Explanation: Ans. (b) HistidineRef: Harper's Biochemistry, 30th ed. pg. 340-42* N1 of purine is derived from amino group of aspartate* N3 & N9 are obtained from amide group of glutamine* C4, C5, & N7 of the purine ring of nucleotides are contributed by glycine.