Nucleotide metabolism

• Nucleotides, nucleosides and nucleic acids have specific structures.
• Digestion of nucleic acids involves the breakdown of nucleic acids into their constituent parts.
• De novo synthesis of purine nucleotides involves the creation of purine nucleotides from scratch.
• Salvage pathways of purine nucleotides involve the recycling of purine nucleotides.
• Catabolism of purine nucleotides involves the breakdown of purine nucleotides into their constituent parts.
• Pyrimidine nucleotide biosynthesis involves the creation of pyrimidine nucleotides from scratch.
• Hyperuricemia, chronic elevation of blood uric acid levels, occurs in about 3% of the population as a consequence of impaired excretion of uric acid or overproduction of purines.
• Urate crystals may also appear as kidney stones.
• In the periphery in the extremities, the solubility of uric acid decreases below 37 ° C and mono sodium urate crystals precipitate around the joints and in collagen-rich tissues such as kidney, cartilage, and ear lobe (tumors).
• The most common symptom of gout is arthritic pain in the joints as a result of monosodium urate deposition in cartilaginous tissue and inflammation around these crystals causes gouty arthritis.
• Degradation of pyrimidine nucleotides involves the breakdown of pyrimidine nucleotides into their constituent parts.
• The nucleotides consist of three kinds of building blocks: ribose sugar, purine or pyrimidine bases, and phosphate group.
• Pyrimidine ring is an aromatic organic compound with 2 nitrogens at 1 and 3 position of a six membered ring.
• Purine ring is an aromatic organic compound that consists of a pyrimidine ring and imidazole ring (C3H4N2).
• Pyrimidine bases are Thymine, Uracil and Cytosine.
• Addition of a phosphate group to the nucleoside forms a nucleotide.
• The purine bases are then oxidized to uric acid, which may be absorbed and excreted in the urine.
• There are two main classes of nucleic acids: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).
• The bases in DNA are Adenin, guanin, cytosine, and thymine, while in RNA they are Adenin, guanin, cytosine, and Uracil.
• DNA is the master blueprint for life and constitutes the genetic material in all free-living organisms and most viruses.
• Ingested nucleic acids and nucleotides are degraded in the intestinal tract to mononucleotides, which are then absorbed or converted to purine and pyrimidine bases.
• Nucleic acids comprise four nucleotides A, C, G, and U joined through a backbone of alternating phosphate and ribose sugar residues.
• Nucleic acids are the main information-carrying part of the cell, energy mediators of the cell, and determine the inherited characteristics of every living organism.
• Nucleotides polymerize to form nucleic acids by linking the 3’ hydroxyl group of one nucleotide to the phosphate of another, eliminating one molecule of water (3’-5’ phosphodiester bond).
• DNA provides the genetic information for the cell and is inherently quite stable.
• In the mouth, dietary nucleic acids remain unchanged, while in the stomach, gastric HCl denatures (hydrogen bonds) of nucleic acids.
• Nucleic acids are digested by Deoxyribonuclease (DNAse) / RNAse to generate Nucleotides, which are then degraded by Nucleotidase.
• Nucleotides are degraded into Nucleosides and Phosphate by Nucleotidase, and Nucleosides are further degraded into Bases and Ribose by Nucleosidase.
• RNA is the genetic material of certain viruses and is also found in all living cells, where it plays an important role in certain processes such as the protein synthesis.
• RNA has many roles, including participating in protein synthesis and bringing the appropriate amino acids to the ribosome in accordance to the genetic code on DNA.
• The sugar in DNA is deoxyribose, while in RNA it is ribose, and the hydroxyl group on the ribose causes RNA to be less stable than DNA.
• Purines and Pyrimidines are dietarily nonessential, as nucleic acids are synthesized in the body from intermediates.
• Purines and Pyrimidines are absorbed through the intestinal lumen and are metabolized by intestinal microbial flora, excreted out through feces.
• DNA and RNA have different structures: DNA is double-stranded and RNA is single-stranded, and DNA can be folded like a hairpin and base paired, while RNA cannot.
• Guanin/Xanthine are first converted to Guanosine, then to Xanthine by Guanin Deaminase, then to Uric Acid by Xanthine Oxidase.
• Adenosine/Deoxyadenosine are first converted to Inosine by Adenosine Deaminase, then to Xantine by Purine Nucleotide Phosphorylase.
• Adenosine Deaminase, along with Purine Nucleoside Phosphorylase, is an essential component of the purine salvage pathway.
• Adenosine Deaminase is responsible for the irreversible deamination of adenosine and deoxyadenosine into inosine.
• The Major Pathways of Purine Catabolism include Nucleotide Nucleoside plus phosphate and Nucleoside plus ribose-1-P.
• Adenosine Deaminase is ubiquitously expressed in lymphoid tissues, particularly the thymus, the brain and gastrointestinal tract.