Adenine is an organic purine nitrogenous base having the formula C5H5N5 that complementarily pairs with thymine and uracil in RNA and DNA respectively.
What is Adenine?
Nucleic acids like DNA and RNA are comprised of monomeric nucleotides. Each nucleotide is formed of a 5-Carbon sugar, phosphoric acid, and nitrogenous base. There are 5 nitrogenous bases found in the genetic code; adenine, guanine, cytosine, thymine, and uracil. The nitrogenous are grouped into pyrimidines and purines.
Adenine like other purines is an aromatic heterocyclic compound. It has 2 carbon rings: an imidazole ring and a pyrimidine ring. When it is linked to the deoxyribose sugar by a covalent glycosidic bond then it is called adenine residue.
Adenine vs Guanine
Guanine and Adenine both are purine nucleobases but differ in their structure. Adenine has an amine group at the 6th position and an additional double bond between C-6 and N-1 in its pyrimidine ring. Guanine pairs with cytosine with 3 hydrogen bonds while adenine pairs with thymine in DNA and in RNA it pairs complementary to Uracil with two hydrogen bonds.
Purines are produced as ribonucleotides and are derived from the nucleotide inosine monophosphate (IMP) that is synthesized from amino acids like glutamine, glycine, and aspartic acid, and a ribose phosphate compound. On reaction with ATP produces 5-Phosphoribosyl-1-pyrophosphate (PRPP).
PRRP has been involved in pyrimidine and purine synthesis, NADP and NAD production, and salvage pathways. When PRRP gets converted into 5-phosphoribosyl amine it becomes committed to the purine biosynthesis pathway that occurs cytosol of liver cells in humans. Utilizing energy from Guanosine triphosphate AMP or GMP is produced by conversion of IMP.
The nucleosides of adenine include deoxyadenosine and adenosine. Adenosine on being phosphorylated with 3 phosphoric acid groups generates ATP by oxidation of respiratory substrates. These energy-rich molecules help in generating energy for metabolic activities.
ATPs can be produced by pathways like glycolysis, fermentation, and the Krebs cycle. Other compounds that comprise Adenine include co-factors like FAD and NAD. ATP also forms one of the nucleotide monomeric units that produce a polymer of RNA and dATP formed by the addition of 3 phosphoric acids on deoxyadenosine, which is one of the constituent nucleotides that make up DNA.
Degradation of adenine occurs in several steps, first enzyme purine nucleoside phosphorylase converts adenosine into inosine which in the presence of enzyme xanthine oxidase is converted to hypoxanthine that is finally metabolised into uric acid.
Uric acid is the waste product generated in purine catabolism that is excreted in the form of urine from the human body. This process of exogenous purine degradation occurs in the liver. Enzyme adenine phosphoribosyltransferase aids in the salvaging of adenine formed and in its re-utilisation. Adenine from catabolism may be salvaged and re-used by the catalytic activity of the enzyme adenine .
Biological Function of Adenine
There are 5 primary fundamental nucleobases that comprise the genetic code; these are adenine, cytosine, guanine, uracil and thymine. The sequence of nitrogenous bases constitutes the genetic code in nuclei acids and these specify the particular protein.
Nucleic acids like DNA and RNA perform many significant functions and are vital for survival, heredity and for cellular metabolism. ATP or adenosine triphosphate, the energy currency Required for biological reactions and cellular metabolism is formed when adenosine attaches with three phosphate groups.
Adenine and Health
The end waste product of Purine metabolism is the Uric acid. Purines exists in high quantities in kidney, liver and in other organs.Exogenic purines can be derived from diet like seafood, meat, cauliflower, mushrooms and beans in moderate amounts. If the uric acid levels stay high in the body it can lead to a condition known as Hyperuricemia.
Ingesting a high-purine diet could result in the inflammation in the joints leading to gout and kidney stones. Therefore, people pre-disposed to such conditions are required to follow a low-purine diet. Saturated fats and alcohol consumption obstruct the metabolism of purines so it is advisable to refrain from their consumption.
Albrecht Kossel, a German biochemist discovered and named all the primary 5 bases. Adenine was formerly referred to as vitamin B4.2 as it was considered a vitamin. Later findings suggested that it can be biosynthesized in the body itself so it not considered a vitamin now.