pyrimidine

Examples of pyrimidine in the following topics:

• Inhibiting Essential Metabolite Synthesis

  • Because tetrahydrofolate is essential for purine and pyrimidine synthesis, its deficiency can lead to inhibited production of DNA, RNA and proteins.
  • The second type of antimetabolite antibiotics consist of pyrimidine analogues which mimic the structure of metabolic pyrimidines .
  • Three nucleobases found in nucleic acids, cytosine (C), thymine (T), and uracil (U), are pyrimidine derivatives and the pyrimidine analogues disrupt their formation and consequently disrupt DNA and RNA synthesis.
  • Distinguish between the three main types of antimetabolite antibiotics (antifolates, pyrimidine and purine analogues)

• Purine and Pyrimidine Synthesis

  • Unlike pyrimidines, purines are biologically synthesized as nucleotides and in particular as ribotides.
  • The first three enzymes of pyrimidine biosynthesis are all coded by the same gene in Metazoa.
  • CTP synthase (or CTP synthetase) is an enzyme involved in pyrimidine biosynthesis.
  • This acts to balance the relative amounts of purine and pyrimidine nucleotides.
  • Adenine and guanine are purines and cytosine and thymine are pyrimidines.

• DNA Repair

  • This repair mechanism is often employed when UV exposure causes the formation of pyrimidine dimers.
  • Transition substitution refers to a purine or pyrimidine being replaced by a base of the same kind; for example, a purine such as adenine may be replaced by the purine guanine.
  • Transversion substitution refers to a purine being replaced by a pyrimidine or vice versa; for example, cytosine, a pyrimidine, is replaced by adenine, a purine.

• The Structure and Sequence of DNA

  • The nitrogenous base can be a purine such as adenine (A) and guanine (G), characterized by double-ring structures, or a pyrimidine such as cytosine (C) and thymine (T), characterized by single-ring structures.
  • Only the pairing between a purine and pyrimidine can explain the uniform diameter.
  • That is to say, at each point along the DNA molecule, the two sugar phosphate backbones are always separated by three rings, two from a purine and one from a pyrimidine.
  • Base pairing takes place between a purine and pyrimidine stabilized by hydrogen bonds: A pairs with T via two hydrogen bonds and G pairs with C via three hydrogen bonds.

• DNA and RNA

  • Cytosine, thymine, and uracil are classified as pyrimidines which have a single carbon-nitrogen ring as their primary structure .
  • Bases can be divided into two categories: purines and pyrimidines.
  • Purines have a double ring structure, and pyrimidines have a single ring.

• Types of RNA

  • Adenine (A), guanine (G), and cytosine (C) are present, but instead of thymine (T), a pyrimidine called uracil (U) pairs with adenine.
  • Bases can be divided into two categories: purines and pyrimidines.
  • Purines have a double ring structure, and pyrimidines have a single ring.

• The DNA Double Helix

  • For example, a certain purine can only pair with a certain pyrimidine.

• Biosynthesis and Energy

  • Biosynthetic building blocks utilized by organisms include amino acids, purines, pyrimidines, lipids, sugars, and enzyme cofactors.

• The Primary Structure of DNA

  • The two monocyclic bases shown here are classified as pyrimidines, and the two bicyclic bases are purines.
  • As shown in the following diagram, the sugar component of RNA is ribose, and the pyrimidine base uracil replaces the thymine base of DNA.

• Six-Membered Rings

  • Fully unsaturated six-membered nitrogen heterocycles, such as pyridine, pyrazine, pyrimidine and pyridazine, have stable aromatic rings.
  • The diazines pyrazine, pyrimidine and pyridazine are all weaker bases than pyridine due to the inductive effect of the second nitrogen.
  • A consideration of the polar contributors helps to explain the difference between pyrazine and pyrimidine, but the basicity of pyridazine seems anomalous.