Zamolo Francesca, Wüst Matthias
University of Bonn, Institute of Nutritional and Food Sciences Chair of Food Chemistry, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany.
Chembiochem. 2023 Oct 4;24(19):e202300362. doi: 10.1002/cbic.202300362. Epub 2023 Aug 8.
Pyrazines are ubiquitous in nature - biosynthesized by microorganisms, insects, and plants. Due to their great structural diversity, they own manifold biological functions. Alkyl- and alkoxypyrazines for instance play a key role as semiochemicals, but also as important aroma compounds in foods. Especially 3-alkyl-2-methoxypyrazines (MPs) have been of great research interest. MPs are associated with green and earthy attributes. They are responsible for the distinctive aroma properties of numerous vegetables. Moreover, they have a strong influence on the aroma of wines, in which they are primarily grape-derived. Over the years various methods have been developed and implemented to analyse the distribution of MPs in plants. In addition, the biosynthetic pathway of MPs has always been of particular interest. Different pathways and precursors have been proposed and controversially discussed in the literature. While the identification of genes encoding O-methyltransferases gave important insights into the last step of MP-biosynthesis, earlier biosynthetic steps and precursors remained unknown. It was not until 2022 that in vivo feeding experiments with stable isotope labeled compounds revealed l-leucine and l-serine as important precursors for IBMP. This discovery gave evidence for a metabolic interface between the MP-biosynthesis and photorespiration.
吡嗪在自然界中广泛存在，由微生物、昆虫和植物进行生物合成。由于其结构多样性极高，它们具有多种生物学功能。例如，烷基和烷氧基吡嗪作为信息素发挥关键作用，同时也是食品中的重要香气化合物。特别是3-烷基-2-甲氧基吡嗪（MPs）一直是研究的热点。MPs具有绿色和泥土气息的特征。它们赋予了众多蔬菜独特的香气特性。此外，它们对葡萄酒的香气有很大影响，葡萄酒中的MPs主要来源于葡萄。多年来，人们开发并采用了各种方法来分析MPs在植物中的分布。此外，MPs的生物合成途径一直备受关注。文献中提出了不同的途径和前体，并进行了有争议的讨论。虽然编码O-甲基转移酶的基因的鉴定为MP生物合成的最后一步提供了重要见解，但早期的生物合成步骤和前体仍然未知。直到2022年，使用稳定同位素标记化合物进行的体内喂养实验才揭示L-亮氨酸和L-丝氨酸是异丁基甲氧基吡嗪（IBMP）的重要前体。这一发现为MP生物合成与光呼吸之间的代谢界面提供了证据。
