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→脂肪酸，类异戊二烯和固醇
=== 脂肪酸，类异戊二烯和固醇 ===
=== 脂肪酸，类异戊二烯和固醇 ===
[[File:Sterol synthesis.svg|thumb|right|upright=1.6|具有中间体异戊烯基焦磷酸酯（IPP），二甲基烯丙基焦磷酸酯（DMAPP），香叶基焦磷酸酯（GPP）和角鲨烯的类固醇合成途径的简化版本。为了清晰起见，省略了一些中间步骤。]]
[[File:Sterol synthesis.svg|thumb|right|upright=1.6|300px|具有中间体异戊烯基焦磷酸酯（IPP），二甲基烯丙基焦磷酸酯（DMAPP），香叶基焦磷酸酯（GPP）和角鲨烯的类固醇合成途径的简化版本。为了清晰起见，省略了一些中间步骤。]]
脂肪酸是由脂肪酸合成酶聚合并还原乙酰辅酶A单元制成的。脂肪酸中的酰基链通过一些反应的循环得以延伸，这些反应包括:添加酰基，将其还原为醇，脱水成烯烃基团，然后再还原为烷烃基团。脂肪酸生物合成的酶可以分为两类：在动物和真菌中，所有脂肪酸合成酶的反应都是由单一的多功能I型蛋白来完成的<ref>{{cite journal | vauthors = Chirala SS, Wakil SJ | title = Structure and function of animal fatty acid synthase | journal = Lipids | volume = 39 | issue = 11 | pages = 1045–53 | date = November 2004 | pmid = 15726818 | doi = 10.1007/s11745-004-1329-9 }}</ref>，而在植物的质体和细菌中，则由单独的II型酶来完成每一步<ref>{{cite journal | vauthors = White SW, Zheng J, Zhang YM | title = The structural biology of type II fatty acid biosynthesis | journal = Annual Review of Biochemistry | volume = 74 | issue = | pages = 791–831 | year = 2005 | pmid = 15952903 | doi = 10.1146/annurev.biochem.74.082803.133524 }}</ref><ref>{{cite journal | vauthors = Ohlrogge JB, Jaworski JG | title = Regulation of Fatty Acid Synthesis | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 48 | issue = | pages = 109–136 | date = June 1997 | pmid = 15012259 | doi = 10.1146/annurev.arplant.48.1.109 }}</ref>。
脂肪酸是由脂肪酸合成酶聚合并还原乙酰辅酶A单元制成的。脂肪酸中的酰基链通过一些反应的循环得以延伸，这些反应包括:添加酰基，将其还原为醇，脱水成烯烃基团，然后再还原为烷烃基团。脂肪酸生物合成的酶可以分为两类：在动物和真菌中，所有脂肪酸合成酶的反应都是由单一的多功能I型蛋白来完成的<ref>{{cite journal | vauthors = Chirala SS, Wakil SJ | title = Structure and function of animal fatty acid synthase | journal = Lipids | volume = 39 | issue = 11 | pages = 1045–53 | date = November 2004 | pmid = 15726818 | doi = 10.1007/s11745-004-1329-9 }}</ref>，而在植物的质体和细菌中，则由单独的II型酶来完成每一步<ref>{{cite journal | vauthors = White SW, Zheng J, Zhang YM | title = The structural biology of type II fatty acid biosynthesis | journal = Annual Review of Biochemistry | volume = 74 | issue = | pages = 791–831 | year = 2005 | pmid = 15952903 | doi = 10.1146/annurev.biochem.74.082803.133524 }}</ref><ref>{{cite journal | vauthors = Ohlrogge JB, Jaworski JG | title = Regulation of Fatty Acid Synthesis | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 48 | issue = | pages = 109–136 | date = June 1997 | pmid = 15012259 | doi = 10.1146/annurev.arplant.48.1.109 }}</ref>。
萜烯和异戊二烯是一大类脂类，包括类胡萝卜素，也是最大的一类植物天然产品<ref>{{cite journal | vauthors = Dubey VS, Bhalla R, Luthra R | title = An overview of the non-mevalonate pathway for terpenoid biosynthesis in plants | journal = Journal of Biosciences | volume = 28 | issue = 5 | pages = 637–46 | date = September 2003 | pmid = 14517367 | doi = 10.1007/BF02703339 | url = http://www.ias.ac.in/jbiosci/sep2003/637.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070415213325/http://www.ias.ac.in/jbiosci/sep2003/637.pdf | df = | archive-date = 15 April 2007 }}</ref>。这些化合物是由反应性前体焦磷酸异戊烯酯和焦磷酸二甲基烯丙基酯所提供的异戊二烯单元组装和改性而成。这些前体可以靠不同的途径制造<ref name=Kuzuyama>{{cite journal | vauthors = Kuzuyama T, Seto H | title = Diversity of the biosynthesis of the isoprene units | journal = Natural Product Reports | volume = 20 | issue = 2 | pages = 171–83 | date = April 2003 | pmid = 12735695 | doi = 10.1039/b109860h }}</ref>。在动物和古生物中，甲戊二酸途径从乙酰辅酶A产生这些化合物<ref>{{cite journal | vauthors = Grochowski LL, Xu H, White RH | title = Methanocaldococcus jannaschii uses a modified mevalonate pathway for biosynthesis of isopentenyl diphosphate | journal = Journal of Bacteriology | volume = 188 | issue = 9 | pages = 3192–8 | date = May 2006 | pmid = 16621811 | pmc = 1447442 | doi = 10.1128/JB.188.9.3192-3198.2006 }}</ref>，而在植物和细菌中，非甲戊二酸途径使用丙酮酸和甘油醛3-磷酸作为底物。使用这些活化的异戊二烯供体的一个重要反应是固醇的生物合成<ref name=Kuzuyama/><ref>{{cite journal | vauthors = Lichtenthaler HK | title = The 1-Deoxy-D-Xylulose-5-Phosphate Pathway of Isoprenoid Biosynthesis in Plants | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 50 | issue = | pages = 47–65 | date = June 1999 | pmid = 15012203 | doi = 10.1146/annurev.arplant.50.1.47 }}</ref>。在该反应中，异戊二烯单元连接在一起，制成角鲨烯，然后折叠起来形成一组环，制成羊毛固醇<ref name=Schroepfer>{{cite journal | vauthors = Schroepfer GJ | title = Sterol biosynthesis | journal = Annual Review of Biochemistry | volume = 50 | issue = | pages = 585–621 | year = 1981 | pmid = 7023367 | doi = 10.1146/annurev.bi.50.070181.003101 }}</ref>。羊毛固醇随后可转化为其他固醇，如胆固醇和麦角固醇<ref name=Schroepfer/><ref>{{cite journal | vauthors = Lees ND, Skaggs B, Kirsch DR, Bard M | title = Cloning of the late genes in the ergosterol biosynthetic pathway of Saccharomyces cerevisiae--a review | journal = Lipids | volume = 30 | issue = 3 | pages = 221–6 | date = March 1995 | pmid = 7791529 | doi = 10.1007/BF02537824 }}</ref>。
萜烯和异戊二烯是一大类脂类，包括类胡萝卜素，也是最大的一类植物天然产品<ref>{{cite journal | vauthors = Dubey VS, Bhalla R, Luthra R | title = An overview of the non-mevalonate pathway for terpenoid biosynthesis in plants | journal = Journal of Biosciences | volume = 28 | issue = 5 | pages = 637–46 | date = September 2003 | pmid = 14517367 | doi = 10.1007/BF02703339 | url = http://www.ias.ac.in/jbiosci/sep2003/637.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070415213325/http://www.ias.ac.in/jbiosci/sep2003/637.pdf | df = | archive-date = 15 April 2007 }}</ref>。这些化合物是由反应性前体焦磷酸异戊烯酯和焦磷酸二甲基烯丙基酯所提供的异戊二烯单元组装和改性而成。这些前体可以靠不同的途径制造<ref name=Kuzuyama>{{cite journal | vauthors = Kuzuyama T, Seto H | title = Diversity of the biosynthesis of the isoprene units | journal = Natural Product Reports | volume = 20 | issue = 2 | pages = 171–83 | date = April 2003 | pmid = 12735695 | doi = 10.1039/b109860h }}</ref>。在动物和古生物中，甲戊二酸途径从乙酰辅酶A产生这些化合物<ref>{{cite journal | vauthors = Grochowski LL, Xu H, White RH | title = Methanocaldococcus jannaschii uses a modified mevalonate pathway for biosynthesis of isopentenyl diphosphate | journal = Journal of Bacteriology | volume = 188 | issue = 9 | pages = 3192–8 | date = May 2006 | pmid = 16621811 | pmc = 1447442 | doi = 10.1128/JB.188.9.3192-3198.2006 }}</ref>，而在植物和细菌中，非甲戊二酸途径使用丙酮酸和甘油醛3-磷酸作为底物。使用这些活化的异戊二烯供体的一个重要反应是固醇的生物合成<ref name=Kuzuyama/><ref>{{cite journal | vauthors = Lichtenthaler HK | title = The 1-Deoxy-D-Xylulose-5-Phosphate Pathway of Isoprenoid Biosynthesis in Plants | journal = Annual Review of Plant Physiology and Plant Molecular Biology | volume = 50 | issue = | pages = 47–65 | date = June 1999 | pmid = 15012203 | doi = 10.1146/annurev.arplant.50.1.47 }}</ref>。在该反应中，异戊二烯单元连接在一起，制成角鲨烯，然后折叠起来形成一组环，制成羊毛固醇<ref name=Schroepfer>{{cite journal | vauthors = Schroepfer GJ | title = Sterol biosynthesis | journal = Annual Review of Biochemistry | volume = 50 | issue = | pages = 585–621 | year = 1981 | pmid = 7023367 | doi = 10.1146/annurev.bi.50.070181.003101 }}</ref>。羊毛固醇随后可转化为其他固醇，如胆固醇和麦角固醇<ref name=Schroepfer/><ref>{{cite journal | vauthors = Lees ND, Skaggs B, Kirsch DR, Bard M | title = Cloning of the late genes in the ergosterol biosynthetic pathway of Saccharomyces cerevisiae--a review | journal = Lipids | volume = 30 | issue = 3 | pages = 221–6 | date = March 1995 | pmid = 7791529 | doi = 10.1007/BF02537824 }}</ref>。
=== 蛋白质类 ===
=== 蛋白质类 ===