Biosynthesis of the flavour precursors of onion and garlic
Biosynthesis of the flavour precursors of onion and garlic
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DOI：
10.1093/jxb/erh138
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发表时间：
2004-08-01
影响因子：
6.9
通讯作者：
Collin, HA
中科院分区：
文献类型：
--
作者：
Jones, MG;Hughes, J;Collin, HA
洋葱（Allium cepa）、大蒜（A. sativum）和其他葱属植物很重要，因为它们的味道和气味具有烹饪价值。这些是每个物种的特征，是通过一系列挥发性硫化合物的化学转化而产生的，这些挥发性硫化合物是通过蒜氨酸酶和催泪因子合酶裂解相对稳定、无味的S-烷（烯）基半胱氨酸亚砜风味前体而产生的。这些次生代谢物是 S-甲基半胱氨酸亚砜（MCSO，蛋氨酸；存在于大多数葱属和一些十字花科植物中）、S-烯丙基半胱氨酸亚砜（ACSO，蒜氨酸；大蒜的特征）、S-反丙-1-烯基半胱氨酸亚砜（PECSO，异蒜氨酸；洋葱的特征）和 S-丙基半胱氨酸亚砜（PCSO，丙氨酸；洋葱及相关产品中的特征）种）。来自假定生物合成中间体转化、放射性标记的研究以及洋葱和大蒜中硫化合物的测量的信息提供了建议生物合成途径的信息。这可能涉及谷胱甘肽中半胱氨酸的烷基（烯）化，然后裂解和氧化以形成烷基（烯）基半胱氨酸亚砜风味前体。还有证据表明，风味前体的合成可能涉及半胱氨酸或前体（例如 O-乙酰丝氨酸）的（硫代）烷（烯）化。这两种途径都可能发生，具体取决于组织的生理状态。环境因素（例如硫的可用性）的影响表明，对每种风味前体的生物合成的控制可能不同。讨论半胱氨酸和谷胱甘肽代谢以表明与葱风味前体生物合成的相似之处。最后，提出了探索确定烷基（烯）基在植物中的起源的可能途径。
Onion (Allium cepa), garlic (A. sativum) and other Alliums are important because of the culinary value of their flavours and odours. These are characteristic of each species and are created by chemical transformation of a series of volatile sulphur compounds generated by cleavage of relatively stable, odourless, S-alk(en)yl cysteine sulphoxide flavour precursors by the enzymes alliinase and lachrymatory-factor synthase. These secondary metabolites are S-methyl cysteine sulphoxide (MCSO, methiin; present in most Alliums, some Brassicaceae), S-allyl cysteine sulphoxide (ACSO, alliin; characteristic of garlic), S-transprop-1-enyl cysteine sulphoxide (PECSO, isoalliin; characteristic of onion), and S-propyl cysteine sulphoxide (PCSO, propiin; in onion and related species). Information from studies of the transformation of putative biosynthetic intermediates, radiolabelling, and from measurements of sulphur compounds within onion and garlic have provided information to suggest a biosynthetic pathway. This may involve alk(en)ylation of the cysteine in glutathione, followed by cleavage and oxidation to form the alk(en)yl cysteine sulphoxide flavour precursors. There is also evidence that synthesis of the flavour precursors may involve (thio)alk(en)ylation of cysteine or a precursor such as O-acetyl serine. Both routes may occur depending on the physiological state of the tissue. There are indications from the effects of environmental factors, such as the availability of sulphur, that control of the biosynthesis of each flavour precursor may be different. Cysteine and glutathione metabolism are discussed to indicate parallels with Allium flavour precursor biosynthesis. Finally, possible avenues for exploration to determine the origin in planta of the alk(en)yl groups are suggested.