Analysis of the Initial Reactions of Plant Fatty Acid Synthesis

植物中的脂肪酸生物合成是提供在膜和植物油的脂质中发现的脂肪酰基组分所必需的主要代谢途径。由于在菠菜中发现了一种新的缩合酶，3-酮脂酰-ACP合成酶II（KAS III），该途径的初始反应顺序正在重新评估中。KAS III在体外具有与其作为催化脂肪酸合成的初始引发反应的酶一致的性质。该提案的目的是获得体内证据，证明它是脂肪酸合成的重要组成部分，通常用于催化初始缩合。此外，将重新评价乙酰辅酶A-ACP转酰酶和KAS I的代谢作用。以前，这两种酶被认为是启动脂肪酸合成。待完成的KAS III的生化表征包括底物特异性和与KAS III共纯化的乙酰辅酶A-ACP转酰酶活性水平。将评估对脂肪酸合成速率和调节的影响。此外，将使用分离的叶绿体评价KAS III和乙酰辅酶A-ACP转酰酶的体内作用。这一建议的结果将有助于确定植物中脂肪酸生物合成的初始步骤。

Fatty acid biosynthesis in plants is a primary metabolic pathway that is necessary to provide the fatty acyl components found in the lipids of membranes and vegetable oils. The initial sequence of reaction for this pathway are under reevaluation since a new condensing enzyme, 3-ketoacyl-ACP synthase II (KAS III), was discovered in spinach. KAS III has properties in vitro that are consistent with it being the enzyme that catalyzes the initial priming reaction of fatty acid synthesis. The objective of this proposal is to obtain in vivo evidence that it is an essential component of fatty acid synthesis and normally acts to catalyze the initial condensation. In addition, the metabolic role of acetyl- CoA-ACP transacylase and KAS I will be reevaluated. Previously, these two enzymes were thought to initiate fatty acid synthesis. The biochemical characterization of KAS III to be completed includes substrate specificity and level of acetyl-CoA-ACP transacylase activity copurifying with KAS III. The effects on rates of, and regulation of fatty acid synthesis will be evaluated. IN addition, the in vivo role of KAS III and acetyl-CoA-ACP transacylase will be evaluated using isolated chloroplasts. The results of this proposal should help to determine the initial steps of fatty acid biosynthesis in plants.//