:Ornithine transcarbamylasedeficiency
The purine andpyrimidine bases of the nucleotide units are not present in the backbonestructure but constitute distinctive side chains, just as the R groups of aminoacid residues are the distinctive side chains of polypeptides.
BIOSYNTHESIS AND CATABOLISM OF PYRIMIDINE NUCLEOTIDES.

Photo provided by Flickr
There are 4 purines and 4pyrimidines that are of concern to us.
Increased amounts of orotic acid in urine are also found in hereditary orotic aciduria (an inborn error of pyrimidine synthesis) (s), in cases of ornithine transcarbamylase deficiency (3), and in patients who are being treatedwith the anti-neoplasticdrug, 6-azauridine (4).
Ornithine transcarbamylase deficiency - Wikipedia
Ornithine transcarbamylase deficiency(OTCD),(note: for students studying for their TJE, try using a morereliable source than wiki) the most common of the , is a rare metabolic disorder, occurring in one outof every 80,000 births. OTCD is a resulting in amutated and ineffective form of the enzyme .

Photo provided by Flickr
Ornithine transcarbamylase deficiency : Wikis (The Full …
For purines, especially, non-hepatic tissues rely heavily on preformedbases - those salvaged from their own intracellular turnover supplemented bybases synthesized in the liver and delivered to tissues via the blood.
regulated pyrimidine biosynthesis
For purines, especially, non-hepatic tissues relyheavily on preformed bases - those salvaged from their own intracellularturnover supplemented by bases synthesized in the liver and delivered totissues via the blood.
DNA analysis of ornithine transcarbamylase deficiency
Indeed, the ability to salvage nucleotides fromsources within the body alleviates any nutritional requirement for nucleotides,thus the purine and pyrimidine bases are not required in the diet.