| 词条 | Valine |
| 释义 |
| Watchedfields = changed | verifiedrevid = 470627961 | Name = Valine | ImageFileL1 = Valin - Valine.svg | ImageFileR1 = Valine at 7.4 pH.png | IUPACName = Valine | OtherNames = 2-Amino-3-methylbutanoic acid |Section1={{Chembox Identifiers | IUPHAR_ligand = 4794 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 6050 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 4CA13A832H | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 43068 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = D00039 | InChI = 1/C5H11NO2/c1-3(2)4(6)5(7)8/h3-4H,6H2,1-2H3,(H,7,8)/t4-/m0/s1 | InChIKey = KZSNJWFQEVHDMF-BYPYZUCNBW | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C5H11NO2/c1-3(2)4(6)5(7)8/h3-4H,6H2,1-2H3,(H,7,8)/t4-/m0/s1 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = KZSNJWFQEVHDMF-BYPYZUCNSA-N | CASNo = 516-06-3 | CASNo_Ref = {{cascite|correct|CAS}} | CASNo1 =72-18-4 | CASNo1_Comment = (L-isomer) | CASNo1_Ref = {{cascite|correct|CAS}} | CASNo2 = 640-68-6 | CASNo2_Comment = (D-isomer) | CASNo2_Ref = {{cascite|correct|CAS}} | EC_number = 208-220-0 | PubChem = 1182 | DrugBank_Ref = {{drugbankcite|correct|drugbank}} | DrugBank = DB00161 | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 57762 | SMILES = CC(C)[C@@H](C(=O)O)N | SMILES1 = CC(C)[C@@H](C(=O)[O-])[NH3+] | SMILES1_Comment = Zwitterion }} |Section2={{Chembox Properties | Properties_ref = [1] | C=5 | H=11 | N=1 | O=2 | Appearance = | Density = 1.316 g/cm3 | MeltingPtC = 298 | MeltingPt_notes = (decomposition) | Solubility = soluble | pKa =2.32 (carboxyl), 9.62 (amino)[2] | MagSus = -74.3·10−6 cm3/mol |Section7={{Chembox Hazards | FlashPt = }} Valine (symbol Val or V)[3] is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isopropyl group, making it a non-polar aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes. It is encoded by all codons starting with GU (GUU, GUC, GUA, and GUG). Like leucine and isoleucine, valine is a branched-chain amino acid. In sickle-cell disease, a single glutamic acid in β-globin is replaced with valine. Because valine is hydrophobic, whereas glutamic acid is hydrophilic, this change makes the hemoglobin prone to abnormal aggregation. History and etymologyValine was first isolated from casein in 1901 by Hermann Emil Fischer.[4] The name valine comes from valeric acid, which in turn is named after the plant valerian due to the presence of the acid in the roots of the plant.[5][6] NomenclatureAccording to IUPAC, carbon atoms forming valine are numbered sequentially starting from 1 denoting the carboxyl carbon, whereas 4 and 4' denote the two terminal methyl carbons.[7] MetabolismSource and biosynthesisValine, like other branched-chain amino acids, is synthesized by plants, but not by animals.[8] It is therefore an essential amino acid in animals, and needs to be present in the diet. Adult humans require about 4 mg/kg body weight daily.[9] 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 α-ketoisovalerate undergoes reductive amination with glutamate. Enzymes involved in this biosynthesis include:[10]
DegradationLike other branched-chain amino acids, the catabolism of valine starts with the removal of the amino group by transamination, giving alpha-ketoisovalerate, an alpha-keto acid, which is converted to isobutyryl-CoA through oxidative decarboxylation by the branched-chain α-ketoacid dehydrogenase complex.[11] This is further oxidised and rearranged to succinyl-CoA, which can enter the citric acid cycle. SynthesisRacemic valine can be synthesized by bromination of isovaleric acid followed by amination of the α-bromo derivative[12]HO2CCH2CH(CH3)2 + Br2 → HO2CCHBrCH(CH3)2 + HBr HO2CCHBrCH(CH3)2 + 2 NH3 → HO2CCH(NH2)CH(CH3)2 + NH4Br Medical SignificanceInsulin resistanceValine, like other branched-chain amino acids, is associated with insulin resistance: higher levels of valine are observed in the blood of diabetic mice, rats, and humans.[13] Mice fed a valine deprivation diet for one day have improved insulin sensitivity, and feeding of a valine deprivation diet for one week significantly decreases blood glucose levels.[14] In diet-induced obese and insulin resistant mice, a diet with decreased levels of valine and the other branched-chain amino acids results in reduced adiposity and improved insulin sensitivity.[15] The valine catabolite 3-hydroxyisobutyrate promotes skeletal muscle insulin resistance in mice by stimulating fatty acid uptake into muscle and lipid accumulation.[16] In humans, a protein restricted diet lowers blood levels of valine and decreases fasting blood glucose levels.[17] Hematopoietic stem cellsDietary valine is essential for hematopoietic stem cell (HSC) self-renewal, as demonstrated by experiments in mice.[18] Dietary valine restriction selectively depletes long-term repopulating HSC in mouse bone marrow. Successful stem cell transplantation was achieved in mice without irradiation after 3 weeks on a valine restricted diet. Long term survival of the transplanted mice was achieved when valine was returned to the diet gradually over a 2-week period to avoid refeeding syndrome. See also
References1. ^{{RubberBible62nd|page=C-569}} 2. ^Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959. 3. ^{{cite web| url = http://www.chem.qmul.ac.uk/iupac/AminoAcid/AA1n2.html | title = Nomenclature and Symbolism for Amino Acids and Peptides | publisher = IUPAC-IUB Joint Commission on Biochemical Nomenclature | year = 1983 | accessdate = 5 March 2018| archiveurl= https://web.archive.org/web/20081009023202/http://www.chem.qmul.ac.uk/iupac/AminoAcid/AA1n2.html| archivedate= 9 October 2008 | deadurl= no}} 4. ^{{cite web |url=http://www.britannica.com/EBchecked/topic/622178/valine |title=valine |work=Encyclopædia Britannica Online |accessdate=2015-12-06}} 5. ^{{cite web |url=http://www.merriam-webster.com/dictionary/valine |title=valine |work=Merriam-Webster Online Dictionary |accessdate=2015-12-06}} 6. ^{{cite web |url=http://www.merriam-webster.com/dictionary/valeric+acid |title=valeric acid |work=Merriam-Webster Online Dictionary |accessdate=2015-12-06}} 7. ^{{cite book| editor-last = Jones| editor-first = J. H.| title = Amino Acids, Peptides and Proteins| publisher = Royal Society of Chemistry| series = Specialist Periodical Reports| volume = 16| location = London| date = 1985| page = 389| isbn = 978-0-85186-144-9 }} 8. ^{{Cite book|url=https://books.google.com/books?id=shDYCwAAQBAJ&pg=PA159|title=Nitrogen metabolism in rice|last=Basuchaudhuri|first=Pranab|publisher=CRC Press|year=2016|isbn=9781498746687|location=Boca Raton, Florida|pages=159|oclc=945482059}} 9. ^{{cite book | last1 = 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 | url = https://www.nap.edu/read/10490/chapter/12}} 10. ^{{Lehninger3rd}}. 11. ^{{Cite book|url=|title=Biochemistry|last=Mathews|first=Christopher K.,|date=2000|publisher=Benjamin Cummings|others=Van Holde, K. E., Ahern, Kevin G.|year=|isbn=0805330666|edition=3rd|location=San Francisco, Calif.|pages=776|oclc=42290721}} 12. ^{{OrgSynth | last = Marvel | first = C. S. | title = dl-Valine | prep = CV3P0848 | volume = 20 | page = 106 | year = 1940 | collvol = 3 | collvolpages = 848}}. 13. ^{{Cite journal|last=Lynch|first=Christopher J.|last2=Adams|first2=Sean H.|date=2014-12-01|title=Branched-chain amino acids in metabolic signalling and insulin resistance|journal=Nature Reviews. Endocrinology|volume=10|issue=12|pages=723–736|doi=10.1038/nrendo.2014.171|issn=1759-5037|pmc=4424797|pmid=25287287}} 14. ^{{Cite journal|last=Xiao|first=Fei|last2=Yu|first2=Junjie|last3=Guo|first3=Yajie|last4=Deng|first4=Jiali|last5=Li|first5=Kai|last6=Du|first6=Ying|last7=Chen|first7=Shanghai|last8=Zhu|first8=Jianmin|last9=Sheng|first9=Hongguang|date=2014-06-01|title=Effects of individual branched-chain amino acids deprivation on insulin sensitivity and glucose metabolism in mice|journal=Metabolism: Clinical and Experimental|volume=63|issue=6|pages=841–850|doi=10.1016/j.metabol.2014.03.006|issn=1532-8600|pmid=24684822}} 15. ^{{Cite journal|last=Cummings|first=Nicole E.|last2=Williams|first2=Elizabeth M.|last3=Kasza|first3=Ildiko|last4=Konon|first4=Elizabeth N.|last5=Schaid|first5=Michael D.|last6=Schmidt|first6=Brian A.|last7=Poudel|first7=Chetan|last8=Sherman|first8=Dawn S.|last9=Yu|first9=Deyang|date=2017-12-19|title=Restoration of metabolic health by decreased consumption of branched-chain amino acids|journal=The Journal of Physiology|doi=10.1113/JP275075|issn=1469-7793|pmid=29266268}} 16. ^{{Cite journal|last=Jang|first=Cholsoon|last2=Oh|first2=Sungwhan F.|last3=Wada|first3=Shogo|last4=Rowe|first4=Glenn C.|last5=Liu|first5=Laura|last6=Chan|first6=Mun Chun|last7=Rhee|first7=James|last8=Hoshino|first8=Atsushi|last9=Kim|first9=Boa|date=2016-04-01|title=A branched-chain amino acid metabolite drives vascular fatty acid transport and causes insulin resistance|journal=Nature Medicine|volume=22|issue=4|pages=421–426|doi=10.1038/nm.4057|issn=1546-170X|pmid=26950361|pmc=4949205}} 17. ^{{Cite journal|last=Fontana|first=Luigi|last2=Cummings|first2=Nicole E.|last3=Arriola Apelo|first3=Sebastian I.|last4=Neuman|first4=Joshua C.|last5=Kasza|first5=Ildiko|last6=Schmidt|first6=Brian A.|last7=Cava|first7=Edda|last8=Spelta|first8=Francesco|last9=Tosti|first9=Valeria|date=2016-06-21|title=Decreased Consumption of Branched-Chain Amino Acids Improves Metabolic Health|journal=Cell Reports|doi=10.1016/j.celrep.2016.05.092|issn=2211-1247|pmid=27346343|pmc=4947548|volume=16|pages=520–30}} 18. ^{{Cite journal|last=Taya|first=Yuki|last2=Ota|first2=Yasunori|last3=Wilkinson|first3=Adam C.|last4=Kanazawa|first4=Ayano|last5=Watarai|first5=Hiroshi|last6=Kasai|first6=Masataka|last7=Nakauchi|first7=Hiromitsu|last8=Yamazaki|first8=Satoshi|date=2016-12-02|title=Depleting dietary valine permits nonmyeloablative mouse hematopoietic stem cell transplantation|journal=Science|volume=354|issue=6316|pages=1152–1155|doi=10.1126/science.aag3145}} External links
6 : Branched-chain amino acids|Proteinogenic amino acids|Glucogenic amino acids|Essential amino acids|Isobutyrates|Isopropyl compounds |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。