• Purine is a heterocyclic aromatic organic compound that consists of a pyrimidine ring fused to an imidazole ring. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines and their tautomers.


  • Pyrimidine is an aromatic heterocyclic organic compound similar to pyridine. One of the three diazines, it has the nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine and pyridazine. In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine, thymine, and uracil.


  • any of the class of simple sugars whose molecules contain five carbon atoms, such as ribose and xylose. They generally have the chemical formula C5H10O5.


  • Ribose is a carbohydrate with the formula C₅H₁₀O₅; specifically, it is a pentose monosaccharide with linear form H−−(CHOH)₄−H, which has all the hydroxyl groups on the same side in the Fischer projection. The term may refer to either of two enantiomers.


  • Nucleotides are the building blocks of the nucleic acid- DNA and RNA


  • dNTPs are made from ribonucleoside diphosphates.


  • Phosphoribosylamine is an intermediate in purine metabolism. It is a precursor to IMP. It is generated from Phosphoribosyl pyrophosphate.


  • Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine. In DNA, guanine is paired with cytosine. The guanine nucleoside is called guanosine.

Adenine Nucleotides

  • Adenine is one of the two purine nucleobases (the other being guanine) used in forming nucleotides of the nucleic acids. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. In RNA, which is used for protein synthesis, adenine binds to uracil.

Carbamoyl Phosphate

  • Carbamoyl phosphate is an anion of biochemical significance. In land-dwelling animals, it is an intermediary metabolite in nitrogen disposal through the urea cycle and the synthesis of pyrimidines.

Carbamoyl Aspartic Acid

  • Carbamoyl aspartic acid is a carbamate derivative which serves as an intermediate in pyrimidine biosynthesis.

Orotidine 5′-phosphate Decarboxylase

  • Orotidine 5′-phosphate decarboxylase or orotidylate decarboxylase is an enzyme involved in pyrimidine biosynthesis. It catalyzes the decarboxylation of orotidine monophosphate to form uridine monophosphate.

Orotidine 5′-Monophosphate

  • Orotidine 5′-monophosphate, also known as orotidylic acid, is a pyrimidine nucleotide which is the last intermediate in the biosynthesis of uridine monophosphate.


  • A nuclease is an enzyme capable of cleaving the phosphodiester bonds between nucleotides of nucleic acids. Nucleases variously effect single and double stranded breaks in their target molecules. In living organisms, they are essential machinery for many aspects of DNA repair.


  • Xanthine is a purine base found in most body tissues and fluids, certain plants, and some urinary calculi. It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine.


  • Hypoxanthine is a naturally occurring purine derivative. It is occasionally found as a constituent of nucleic acids, where it is present in the anticodon of tRNA in the form of its nucleoside inosine. It has a tautomer known as 6-hydroxypurine.


  • It forces salvage and prevents formation of uric acid

Salvage Pathway

  • A salvage pathway is a pathway in which nucleotides (purine and pyrimidine) are synthesized from intermediates in the degradative pathway for nucleotides. Salvage pathways are used to recover bases and nucleosides that are formed during degradation of RNA and DNA.


  • Uracil is one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U. The others are adenine, cytosine, and guanine. In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine. Uracil is a demethylated form of thymine.


  • Thymine is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. In RNA, thymine is replaced by the nucleobase uracil.


  • A deoxyribonucleotide is the monomer, or single unit, of DNA, or deoxyribonucleic acid. Each deoxyribonucleotide comprises three parts: a nitrogenous base, a deoxyribose sugar, and one phosphate group.

Ribonucleotide Reductase

  • Ribonucleotide reductase, also known as ribonucleotide diphosphate reductase, is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides. It catalyzes this formation by removing the 2′-hydroxyl group of the ribose ring of nucleoside diphosphates.

Thymidylate Synthase

  • Thymidylate synthase is an enzyme that catalyzes the conversion of deoxyuridine monophosphate to deoxythymidine monophosphate. Thymidine is one of the nucleotides in DNA. With inhibition of TS, an imbalance of deoxynucleotides and increased levels of dUMP arise. Both cause DNA damage.


  • Dihydrofolic acid (conjugate base dihydrofolate) (DHF) is a folic acid (vitamin B9) derivative which is converted to tetrahydrofolic acid by dihydrofolate reductase.


  • It is a competitive inhibitor of DHFR
  • Methotrexate, formerly known as amethopterin, is a chemotherapy agent and immune system suppressant. It is used to treat cancer, autoimmune diseases, ectopic pregnancy, and for medical abortions.

Nucleoside Analogs

  • Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotides which contain a nucleic acid analogue, a sugar, and one to three phosphate groups.


  • Didanosine, marketed under the trade names Videx, is a medication used to treat HIV/AIDS. It is used in combination with other medications as part of highly active antiretroviral therapy. It is of the reverse-transcriptase inhibitor class.


  • Deoxyadenosine is a deoxyribonucleoside. It is a derivative of the nucleoside adenosine, differing from the latter by the replacement of a hydroxyl group by hydrogen at the 2′ position of its ribose sugar moiety. Deoxyadenosine is the DNA nucleoside A, which pairs with deoxythymidine in double-stranded DNA.


  • Vidarabine or 9-β-D-arabinofuranosyladenine is an antiviral drug which is active against herpes simplex and varicella zoster viruses.


  • Adenosine is both a chemical found in many living systems and a medication. As a medication it is used to treat certain forms of supraventricular tachycardia that do not improve with vagal maneuvers. Common side effects include chest pain, feeling faint, shortness of breath and tingling of the senses.


  • Deoxycytidine is a deoxyribonucleoside, a component of deoxyribonucleic acid. It is similar to the ribonucleoside cytidine, but with one hydroxyl group removed from the 2′ position. Deoxycytidine can be phosphorylated by deoxycytidine kinase.


  • Guanosine is a purine nucleoside comprising guanine attached to a ribose ring via a β-N₉-glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate, cyclic guanosine monophosphate, guanosine diphosphate, and guanosine triphosphate.


  • Thymidine is a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine in double-stranded DNA. In cell biology it is used to synchronize the cells in G1/early S phase.


  • Deoxyuridine is a compound and a nucleoside. It is similar in chemical structure to uridine, but without the 2′-hydroxyl group. Idoxuridine and Trifluridine are variants of deoxyuridine used as antiviral drugs.