Editing Purine (section)

== Biochemistry ==
Purines and pyrimidines make up the two groups of [[nitrogenous base]]s, including the two groups of [[nucleotide bases]]. The purine bases are guanine (G) and adenine (A) which form corresponding nucleosides-[[deoxyribonucleoside]]s ([[deoxyguanosine]]  and [[deoxyadenosine]]) with deoxyribose moiety and [[ribonucleoside]]s ([[guanosine]], [[adenosine]]) with ribose moiety. These nucleosides with phosphoric acid form corresponding nucleotides (deoxyguanylate, deoxyadenylate and guanylate, adenylate) which are the building blocks of [[DNA]] and [[RNA]], respectively. Purine bases also play an essential role in many metabolic and signalling processes within the compounds [[guanosine monophosphate]] (GMP) and [[adenosine monophosphate]] (AMP).

In order to perform these essential cellular processes, both purines and pyrimidines are needed by the [[Cell (biology)|cell]], and in similar quantities. Both purine and pyrimidine are self-[[Enzyme inhibitor|inhibiting]] and [[Enzyme activator|activating]]. When purines are formed, they [[Enzyme inhibition|inhibit]] the [[enzyme]]s required for more purine formation. This self-inhibition occurs as they also activate the enzymes needed for pyrimidine formation. Pyrimidine simultaneously self-inhibits and activates purine in a similar manner. Because of this, there is nearly an equal amount of both substances in the cell at all times.<ref>{{Cite book|title=Textbook of Medical Physiology|url=https://archive.org/details/textbookmedicalp00acgu|url-access=limited| vauthors = Guyton AC |publisher=Elsevier|year=2006|isbn=978-0-7216-0240-0 |page=[https://archive.org/details/textbookmedicalp00acgu/page/n71 37]}}</ref>