Biosynthesis of Linoleic Acid in Insects

脊椎动物不能合成，因此需要从食物中获取18:2（n-6）的亚油酸。亚油酸既是膜的结构成分，也是生理上重要的类二十烷酸的前体。直到最近，人们还认为昆虫和脊椎动物一样，不能合成亚油酸。研究表明，一些（但不是全部）昆虫物种具有δ -12去饱和酶，因此能够产生亚油酸。本提案旨在研究亚油酸在蟑螂（美洲大蠊）、蚜虫（Acyrthosiphon pisum）和蟋蟀（Acheta domesticus）中的合成。重点将放在旨在明确排除共生和外部微生物对亚油酸合成的贡献的研究上。这是昆虫组织负责将油酸盐转化为亚油酸盐。此外，还将研究δ -12去饱和酶的底物形式以及亚油酸的进一步延伸和去饱和。这些研究将描述某些昆虫从对多不饱和脂肪酸的膳食需求中获得营养独立性的独特过程。这项工作将获得比较脂质代谢的重要基础知识。亚油酸是脊椎动物必需的脂肪酸。它是一种重要的膜成分，是调节许多细胞功能的激素样物质的前体。脊椎动物缺乏合成亚油酸和通过食用植物来满足其饮食需求的能力，除了原生动物和真菌外，植物也容易合成这种脂肪酸。直到最近，人们还认为昆虫和其他动物一样，不能合成亚油酸。最近的证据表明昆虫确实有这种能力。本研究将检验这一现象。这将提供对昆虫亚油酸生物合成的基本了解，并可能对开发昆虫特异性激素调节途径作为害虫控制手段具有重要意义。

Vertebrates cannot synthesize and thus require a dietary source of linoleic acid, 18:2(n-6), which is used both as a structural component of membranes and as precursor for physiologically important eicosanoids. Until recently, it had been thought that insects, as is the case for vertebrates, were unable to synthesize linoleic acid. Studies have demonstrated that some, but not all, insect species possess a delta-12 desaturase and are thus able to produce linoleic acid. This proposal is designed to examine this synthesis of linoleic acid in the cockroach, Periplaneta americana, the aphid, Acyrthosiphon pisum, and the cricket, Acheta domesticus. Emphasis will be on studies designed to unambiguously rule out the contribution of microorganisms, both symbiotic and exterior, to linoleate synthesis, ie. that it is the insect tissue that is responsible for the desaturation of oleate to linoleate. In addition, the form of the substrate for the delta-12 desaturase and the further elongation and desaturation of linoleic acid will be examined. These studies will characterize the unique process by which certain insect species have gained a nutritional independence from dietary requirements for polyunsaturated fatty acids. Significant fundamental knowledge of comparative lipid metabolism will be obtained from this work. Linoleic acid is an essential fatty acid for vertebrates. It is an important membrane component and serves as a precursor for hormone-like substances that regulate many cell functions. Vertebrates lack the ability to synthesize linoleic acid and fulfill their dietary requirement by the consumption of plants, which, in addition to protozoa and fungi readily synthesize the fatty acid. Until recently, it was thought that insects, like other animals, were unable to synthesize linoleic acid. Recent evidence now suggests that insects do have this capability. This research will examine this phenomenon. It will provide a basic understanding of linoleic acid biosynthesis in insects and may have future implications for the exploitation of the insect-specific pathways of hormone regulation as a means of pest control.