Various atoms of pyrimidine ring are derived from :
1
N1, C4, C5, C6 - Aspartate, C2 - Bicarbonate and N3 - Glutamine
2
N1, C4, C5, C6 - Glutamine, C2 - Bicarbonate and N3 - Aspartate
3
N1, C4, C5, C6 - Aspartate, C2 - Bicarbonate and N3 - Glutamate
4
N1, C4, C5, C6 - Aspargine, C2 - Bicarbonate and N3 - Glutamine