purines and pyrimidines

1. BIOSYNTHESIS OF PURINES &
PYRIMIDINES

2. What is purine biosynthesis
• Purines are biologically synthesized as nucleotides and ribosides, i.e. bases
attached to ribose 5-phosphate. Purine metabolism refers to the metabolic
pathways to synthesize and break down purines that are present in many
organisms.

4. Significance of purine synthesis
Purines serve as building blocks of nucleic acids.
ATP plays an important role in energy transformation.
ATP, ADP, and AMP may function as allosteric regulators and participate in regulation of
many metabolic path-ways.
ATP involves in covalent modification of enzymes. ways.
GMP are secondary messengers.
Salvage pathways are used to recover bases and nucleosides that are formed during
degradation of RNA and DNA.
In comparison to de novo pathway, salvage pathway is energy-saving.
In brain and bone marrow tissues salvage pathway is the only pathway of nucleotide
synthesis.

5. What is pyrimidine synthesis
De novo pyrimidine nucleotide biosynthesis which is also referred to as the
orotate pathway is usually defined as the formation of UMP from carbamoyl
phosphate (CP).

7. Significance of pyrimidine synthesis
The action of purine nucleotides on pyrimidine formation is important
because it establishes a balance between the production of both types of
nucleotides, especially for DNA synthesis.