Editing Lysine (section)

== Nutritional value ==
Lysine is an essential amino acid in humans.<ref name="Nelson_2013">{{cite book |title=Lehninger principles of biochemistry | first1 = David L | last1 = Nelson | first2 = Michael M | last2 = Cox | first3 = Albert L | last3 = Lehninger | name-list-style = vanc  |date=2013|publisher=W.H. Freeman and Company |isbn=978-1-4641-0962-1|edition=6th |location=New York|oclc=824794893}}</ref> The human daily nutritional requirement varies from ~60&nbsp;mg/kg in infancy to ~30&nbsp;mg/kg in adults.<ref name="Tomé_2007" /> This requirement is commonly met in a [[Western world|western society]] with the intake of [[#Dietary sources|lysine from meat and vegetable sources]] well in excess of the recommended requirement.<ref name="Tomé_2007" /> In vegetarian diets, the intake of lysine is less due to the limited quantity of lysine in [[Cereal|cereal crops]] compared to meat sources.<ref name="Tomé_2007" />

Given the limiting concentration of lysine in cereal crops, it has long been speculated that the content of lysine can be increased through [[Genetic engineering|genetic modification]] practices.<ref name="Galili_2013">{{cite journal | vauthors = Galili G, Amir R | title = Fortifying plants with the essential amino acids lysine and methionine to improve nutritional quality | journal = Plant Biotechnology Journal | volume = 11 | issue = 2 | pages = 211–222 | date = February 2013 | pmid = 23279001 | doi = 10.1111/pbi.12025 | doi-access = free }}</ref><ref name="Wang_2017">{{cite journal | vauthors = Wang G, Xu M, Wang W, Galili G | title = Fortifying Horticultural Crops with Essential Amino Acids: A Review | journal = International Journal of Molecular Sciences | volume = 18 | issue = 6 | pages = 1306 | date = June 2017 | pmid = 28629176 | pmc = 5486127 | doi = 10.3390/ijms18061306 | doi-access = free }}</ref> Often these practices have involved the intentional dysregulation of the DAP pathway by means of introducing lysine feedback-insensitive [[Sequence homology#Orthology|orthologues]] of the DHDPS enzyme.<ref name="Galili_2013" /><ref name="Wang_2017" /> These methods have met limited success likely due to the [[Toxicity|toxic]] side effects of increased free lysine and indirect effects on the TCA cycle.<ref>{{cite journal | vauthors = Angelovici R, Fait A, Fernie AR, Galili G | title = A seed high-lysine trait is negatively associated with the TCA cycle and slows down Arabidopsis seed germination | journal = The New Phytologist | volume = 189 | issue = 1 | pages = 148–159 | date = January 2011 | pmid = 20946418 | doi = 10.1111/j.1469-8137.2010.03478.x | doi-access = free }}</ref> Plants accumulate lysine and other amino acids in the form of seed [[storage protein]]s, found within the seeds of the plant, and this represents the edible component of cereal crops.<ref>{{cite journal | vauthors = Edelman M, Colt M | title = Nutrient Value of Leaf vs. Seed | journal = Frontiers in Chemistry | volume = 4 | pages = 32 | date = 2016 | pmid = 27493937 | pmc = 4954856 | doi = 10.3389/fchem.2016.00032 | doi-access = free }}</ref> This highlights the need to not only increase free lysine, but also direct lysine towards the synthesis of stable seed storage proteins, and subsequently, increase the nutritional value of the consumable component of crops.<ref>{{cite journal | vauthors = Jiang SY, Ma A, Xie L, Ramachandran S | title = Improving protein content and quality by over-expressing artificially synthetic fusion proteins with high lysine and threonine constituent in rice plants | journal = Scientific Reports | volume = 6 | issue = 1 | pages = 34427 | date = September 2016 | pmid = 27677708 | pmc = 5039639 | doi = 10.1038/srep34427 | bibcode = 2016NatSR...634427J }}</ref><ref name="Shewry_2007">{{Cite journal|last=Shewry|first=Peter R. | name-list-style = vanc |title=Improving the protein content and composition of cereal grain |journal=Journal of Cereal Science | date = November 2007 |volume=46|issue=3|pages=239–250|doi=10.1016/j.jcs.2007.06.006}}</ref> While genetic modification practices have met limited success, more traditional [[selective breeding]] techniques have allowed for the isolation of "[[Quality Protein Maize]]", which has significantly increased levels of lysine and [[tryptophan]], also an essential amino acid. This increase in lysine content is attributed to an ''opaque-2'' mutation that reduced the [[Transcription (biology)|transcription]] of lysine-lacking [[zein]]-related seed storage proteins and, as a result, increased the abundance of other proteins that are rich in lysine.<ref name="Shewry_2007" /><ref>{{Cite journal | vauthors = Prasanna B, Vasal SK, Kassahun B, Singh NN |date=2001|title=Quality protein maize| jstor = 24105845 |journal=Current Science|volume=81|issue=10|pages=1308–1319}}</ref> Commonly, to overcome the limiting abundance of lysine in [[livestock]] feed, industrially produced lysine is added.<ref name="Kircher_2001">{{cite journal | vauthors = Kircher M, Pfefferle W | title = The fermentative production of <small>L</small>-lysine as an animal feed additive | journal = Chemosphere | volume = 43 | issue = 1 | pages = 27–31 | date = April 2001 | pmid = 11233822 | doi = 10.1016/s0045-6535(00)00320-9 | bibcode = 2001Chmsp..43...27K }}</ref><ref>{{Cite journal|last1=Junior|first1=Letti|last2=Alberto|first2=Luiz|last3=Letti|first3=Gilberto Vinícius Melo|last4=Soccol|first4=Carlos Ricardo|last5=Junior|first5=Letti|last6=Alberto|first6=Luiz|last7=Letti|first7=Gilberto Vinícius Melo|last8=Soccol|first8=Carlos Ricardo | name-list-style = vanc |date=2016|title=Development of an <small>L</small>-Lysine Enriched Bran for Animal Nutrition via Submerged Fermentation by Corynebacterium glutamicum using Agroindustrial Substrates|journal=Brazilian Archives of Biology and Technology|volume=59|doi=10.1590/1678-4324-2016150519|issn=1516-8913|doi-access=free}}</ref> The industrial process includes the [[Fermentation|fermentative]] culturing of ''[[Corynebacterium glutamicum]]'' and the subsequent purification of lysine.<ref name="Kircher_2001" />

=== Dietary sources ===
Good sources of lysine are high-protein foods such as eggs, meat (specifically red meat, lamb, pork, and poultry), [[Soy protein|soy]], beans and peas, cheese (particularly Parmesan), and certain fish (such as [[cod]] and [[sardine]]s).<ref>{{cite web|url=http://www.umm.edu/altmed/articles/lysine-000312.htm|title=Lysine|author=University of Maryland Medical Center|access-date=2009-12-30}}</ref> Lysine is the [[Essential amino acid#Protein quality|limiting amino acid]] (the essential amino acid found in the smallest quantity in the particular foodstuff) in most [[cereal grain]]s, but is plentiful in most [[Pulse (legume)|pulses]] (legumes).<ref name="VRYoung">{{cite journal|vauthors=Young VR, Pellett PL|year=1994|title=Plant proteins in relation to human protein and amino acid nutrition|journal=American Journal of Clinical Nutrition|volume=59|issue=5&nbsp;Suppl|pages=1203S–1212S|doi=10.1093/ajcn/59.5.1203s|pmid=8172124|s2cid=35271281|doi-access=free}}</ref> Beans contain the lysine that [[maize]] lacks, and in the human archeological record beans and maize often appear together, as in the [[Three Sisters (agriculture)|Three Sisters]]: beans, maize, and squash.<ref>{{cite journal |title=The 'How' of the Three Sisters: The Origins of Agriculture in Mesoamerica and the Human Niche |first=Amanda J. |last=Landon |url=https://digitalcommons.unl.edu/nebanthro/40/ |accessdate=9 August 2022 |year=2008 |journal=Nebraska Anthropologist |pages=110–124}}</ref>

A food is considered to have sufficient lysine if it has at least 51&nbsp;mg of lysine per gram of protein (so that the protein is 5.1% lysine).<ref>{{cite book|url=https://www.nap.edu/read/10490/chapter/12|title=Dietary Reference Intakes for Macronutrients|author=Institute of Medicine of the National Academies|year=2005|page=589|doi=10.17226/10490|isbn=978-0-309-08525-0|access-date=2017-10-29}}</ref> <small>L</small>-lysine HCl is used as a [[dietary supplement]], providing 80.03% <small>L</small>-lysine.<ref name="DSBI">{{cite web|url=https://www.cdc.gov/nchs/nhanes/nhanes1999-2000/DSBI.htm|title=Dietary Supplement Database: Blend Information (DSBI)|quote=<small>L</small>-Lysine HCl 10000820 80.03% lysine}}</ref> As such, 1&nbsp;g of <small>L</small>-lysine is contained in 1.25&nbsp;g of <small>L</small>-lysine HCl.