Editing Valine (section)

==Metabolism==
===Source and biosynthesis===
Valine, like other branched-chain amino acids, is synthesized by bacteria and plants, but not by animals.<ref>{{Cite book|url=https://books.google.com/books?id=shDYCwAAQBAJ&pg=PA159|title=Nitrogen metabolism in rice| vauthors = Basuchaudhuri P |publisher=CRC Press|year=2016|isbn=978-1-4987-4668-7 |location=Boca Raton, Florida|pages=159|oclc=945482059}}</ref> It is therefore an [[essential amino acid]] in animals, and needs to be present in the diet. Adult humans require about 24&nbsp;mg/kg body weight daily.<ref name="DRItext">{{cite book | last1 = Institute of Medicine | author-link = Institute of Medicine | title = Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids | chapter = Protein and Amino Acids | publisher = The National Academies Press | year = 2002 | location = Washington, DC | pages = 589–768 | chapter-url = https://www.nap.edu/read/10490/chapter/12 | doi = 10.17226/10490 | isbn = 978-0-309-08537-3 }}</ref> It is synthesized in plants and bacteria via several steps starting from [[pyruvic acid]]. The initial part of the pathway also leads to [[leucine]]. The intermediate [[alpha-Ketoisovaleric acid|α-ketoisovalerate]] undergoes [[reductive amination]] with [[glutamate]].  Enzymes involved in this biosynthesis include:<ref>{{Lehninger3rd}}.</ref>
# [[Acetolactate synthase]] (also known as acetohydroxy acid synthase)
# [[Ketol-acid reductoisomerase|Acetohydroxy acid isomeroreductase]]
# [[Dihydroxyacid dehydratase]]
# [[Valine—pyruvate transaminase|Valine aminotransferase]]

=== Degradation ===
Like other branched-chain amino acids, the catabolism of valine starts with the removal of the amino group by [[transamination]], giving [[Alpha-Ketoisovaleric acid|alpha-ketoisovalerate]], an alpha-[[keto acid]], which is converted to [[isobutyryl-CoA]] through [[oxidative decarboxylation]] by the [[Branched-chain alpha-keto acid dehydrogenase complex|branched-chain α-ketoacid dehydrogenase complex]].<ref name=":0">{{Cite book|title=Biochemistry| vauthors = Mathews CK |date=2000|publisher=Benjamin Cummings|others=Van Holde, K. E., Ahern, Kevin G.|isbn=978-0-8053-3066-3 |edition=3rd|location=San Francisco, Calif.|pages=776|oclc=42290721}}</ref> This is further oxidised and rearranged to [[succinyl-CoA]], which can enter the [[citric acid cycle]] and provide direct fuel in muscle tissue.<ref>{{cite web |url=https://www.stanfordchem.com/l-valine.html |title=L-Valine |website=Stanford Chemicals |access-date=Oct 29, 2024}}</ref><ref>{{cite book |last=Kumari |first=Asha |year=2023 |title=Sweet Biochemistry |edition=5th |pages=9–15 |chapter=Chapter 2 - Citric acid cycle |publisher=Academic Press |isbn=9780443153488}}</ref>