Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI, USA.
BMC Biochem. 2010 Aug 24;11:33. doi: 10.1186/1471-2091-11-33.
Filamentous fungi in the genus Aspergillus produce a variety of natural products, including aflatoxin, the most potent naturally occurring carcinogen known. Aflatoxin biosynthesis, one of the most highly characterized secondary metabolic pathways, offers a model system to study secondary metabolism in eukaryotes. To control or customize biosynthesis of natural products we must understand how secondary metabolism integrates into the overall cellular metabolic network. By applying a metabolomics approach we analyzed volatile compounds synthesized by Aspergillus parasiticus in an attempt to define the association of secondary metabolism with other metabolic and cellular processes.
Volatile compounds were examined using solid phase microextraction--gas chromatography/mass spectrometry. In the wild type strain Aspergillus parasiticus SU-1, the largest group of volatiles included compounds derived from catabolism of branched chain amino acids (leucine, isoleucine, and valine); we also identified alcohols, esters, aldehydes, and lipid-derived volatiles. The number and quantity of the volatiles produced depended on media composition, time of incubation, and light-dark status. A block in aflatoxin biosynthesis or disruption of the global regulator veA affected the volatile profile. In addition to its multiple functions in secondary metabolism and development, VeA negatively regulated catabolism of branched chain amino acids and synthesis of ethanol at the transcriptional level thus playing a role in controlling carbon flow within the cell. Finally, we demonstrated that volatiles generated by a veA disruption mutant are part of the complex regulatory machinery that mediates the effects of VeA on asexual conidiation and sclerotia formation.
曲霉菌属中的丝状真菌产生多种天然产物，包括黄曲霉毒素，这是已知最有效的天然致癌物。黄曲霉毒素生物合成是研究真核生物次生代谢途径的典型模型系统之一。为了控制或定制天然产物的生物合成，我们必须了解次生代谢如何与其他代谢和细胞过程整合。通过应用代谢组学方法，我们分析了寄生曲霉（Aspergillus parasiticus）合成的挥发性化合物，试图定义次生代谢与其他代谢和细胞过程的关联。
使用固相微萃取-气相色谱/质谱法检测挥发性化合物。在野生型菌株寄生曲霉 SU-1 中，最大的挥发性化合物组包括支链氨基酸（亮氨酸、异亮氨酸和缬氨酸）代谢产物；我们还鉴定了醇、酯、醛和脂类衍生的挥发性化合物。挥发性化合物的产生数量和种类取决于培养基组成、培养时间和光照-黑暗状态。黄曲霉毒素生物合成的阻断或全局调控因子 veA 的破坏会影响挥发性谱。除了在次生代谢和发育中的多种功能外，VeA 在转录水平上还负调控支链氨基酸的分解代谢和乙醇的合成，从而在细胞内碳流的控制中发挥作用。最后，我们证明了 veA 缺失突变体产生的挥发性化合物是介导 VeA 对无性分生孢子形成和产黑色素体形成影响的复杂调控机制的一部分。
1）挥发性分析提供了一种快速、有效和强大的方法来鉴定丝状真菌细胞内代谢网络的变化。2）VeA 协调次生代谢物的生物合成与支链氨基酸的分解代谢、醇的生物合成和脂肪酸的β-氧化。3）寄生曲霉的细胞内化学发育与形态发育有关。4）了解次生代谢途径和支链氨基酸分解代谢中的碳流对于控制和定制天然产物的生产至关重要。
