Editing Capsaicin (section)

=== History ===
The general biosynthetic pathway of capsaicin and other capsaicinoids was elucidated in the 1960s by Bennett and Kirby, and Leete and Louden. Radiolabeling studies identified phenylalanine and valine as the precursors to capsaicin.<ref>Bennett DJ, Kirby GW (1968) Constitution and biosynthesis of capsaicin. J Chem Soc C 4:442–446</ref><ref name="Leete, E. 1968"/> Enzymes of the [[phenylpropanoid]] pathway, phenylalanine ammonia lyase (PAL), cinnamate 4-hydroxylase (C4H), caffeic acid ''O''-methyltransferase (COMT) and their function in capsaicinoid biosynthesis were identified later by Fujiwake et al.,<ref>{{cite journal | vauthors = Fujiwake H, Suzuki T, Iwai K | title = Intracellular distributions of enzymes and intermediates involved in biosynthesis of capsaicin and its analogues in Capsicum fruits. | journal = Agricultural and Biological Chemistry | date = November 1982 | volume = 46 | issue = 11 | pages = 2685–2689 | doi = 10.1080/00021369.1982.10865495 }}</ref><ref>{{cite journal | vauthors = Fujiwake H, Suzuki T, Iwai K | title = Capsaicinoid formation in the protoplast from the placenta of Capsicum fruits. | journal = Agricultural and Biological Chemistry | date = October 1982 | volume = 46 | issue = 10 | pages = 2591–2592 | doi = 10.1080/00021369.1982.10865477 }}</ref> and Sukrasno and Yeoman.<ref>{{cite journal | vauthors = Sukrasno N, Yeoman MM | year = 1993 | title = Phenylpropanoid metabolism during growth and development of ''Capsicum frutescens'' fruits | journal = Phytochemistry | volume = 32 | issue = 4| pages = 839–844 | doi=10.1016/0031-9422(93)85217-f| bibcode = 1993PChem..32..839S }}</ref> Suzuki et al. are responsible for identifying leucine as another precursor to the branched-chain [[Fatty acid synthesis|fatty acid pathway]].<ref>{{cite journal | vauthors = Suzuki T, Kawada T, Iwai K | year = 1981 | title = Formation and metabolism of pungent principle of ''Capsicum'' fruits. 9. Biosynthesis of acyl moieties of capsaicin and its analogs from valine and leucine in ''Capsicum'' fruits | journal = Plant & Cell Physiology | volume = 22 | pages = 23–32 | doi = 10.1093/oxfordjournals.pcp.a076142 }}</ref> It was discovered in 1999 that pungency of chili peppers is related to higher transcription levels of key enzymes of the phenylpropanoid pathway, phenylalanine ammonia lyase, cinnamate 4-hydroxylase, caffeic acid ''O''-methyltransferase. Similar studies showed high transcription levels in the placenta of chili peppers with high pungency of genes responsible for branched-chain fatty acid pathway.<ref>{{cite journal | vauthors = Curry J, Aluru M, Mendoza M, Nevarez J, Melendrez M, O'Connell MA | year = 1999 | title = Transcripts for possible capsaicinoid biosynthetic genes are differentially accumulated in pungent and non-pungent ''Capsicum'' spp | journal = Plant Sci | volume = 148 | issue = 1 | pages = 47–57 | doi = 10.1016/s0168-9452(99)00118-1 | bibcode = 1999PlnSc.148...47C | s2cid = 86735106 }}</ref>