SECTION 8. METABOLISM OF NUCLEOTIDES

Main subjects:

8.1. Biosynthesis and catabolism of purine nucleotides. Hyperuricemia and gout

8.2. Biosynthesis and catabolism of pyrimidine nucle-otides

8.3. Formation of deoxyribonucleotides

8.4. Enzymes of nucleotide synthesis as targets for antiviral and anticancer drugs

The nucleotides and their derivatives perform various functions.

• The riboand deoxyribotrinucleotides are substrates for DNA and RNA synthesis.

• The ATP-ADP cycle provides the transformation of energy of oxidation to the energy of synthetic processes and other types of cell activities.

• The nucleotide derivatives take part in the synthesis of homoand heteropolysaccharides, lipids and proteins; are used in the universal system of detoxification that ensures the excretion of foreign compounds and end products of metabolism from the body.

• AMP is part of NAD ⁺, NADP⁺, FAD coenzymes of dehydrogenases and the coenzyme of acyla-tion - CoASH.

• cAMP and cGMP are the secondary messengers of hormones, growth factors, eicosanoids, neuro-transmitters and other cell regulatory molecules.

Almost all cells are able to synthesize nucleotides, and this process is the main source of these molecules in the body. The products of splitting (cleavage) of tissue and dietary nucleic acids are used repeatedly only to a small extent.

Phosphoribosyl pyrophosphate (PRPP) occupies the central position in the synthesis of both purine and pyrimidine nucleotides. The PRPP is formed from the riboso-5-phosphate and ATP in the reaction catalyzed by PRPP-synthase:

The sources of the riboso-5-phosphate are the pentose phosphate pathway of glucose oxidation or pen-

toses being formed in tissues during the nucleotide and nucleic acid degradation.