Dieuaide M, Brouquisse R, Pradet A, Raymond P
Institut National de la Recherche Agronomique Centre de Recherche de Bordeaux Station de Physiologie Végétale, BP 81 33883 Villenave d'Ornon, Cedex, France.
Plant Physiol. 1992 Jun;99(2):595-600. doi: 10.1104/pp.99.2.595.
The effects of glucose starvation on the oxidation of fatty acids were studied in excised maize (Zea mays L.) root tips. After 24 hours of glucose starvation, the rate of oxidation of palmitic acid to CO(2) by the root tips was increased 2.5-fold. Different enzyme activities were tested in a crude particulate fraction from nonstarved root tips and those starved for 24 hours. The activities of the beta-oxidation enzymes crotonase, hydroxyacyl-coenzyme A (CoA) dehydrogenase, and thiolase and those of catalase, malate synthase, and peroxisomal citrate synthase were higher after starvation. However, no isocitrate lyase activity was detected, thus suggesting that the glyoxylate cycle does not operate. The overall beta-oxidation activity was assayed as the formation of [(14)C]acetyl-CoA from [(14)C]palmitic acid after high-performance liquid chromatography analysis of the CoA derivatives. An activity was detected in sugar-fed root tips, and it was increased by two-to fivefold in starved roots. Because the recovery of enzyme activities is only marginally better in starved roots compared with nonstarved roots, these results indicate that the beta-oxidation activity in the tissues is increased during sugar starvation. This increase is probably an essential part of the response to a situation in which lipids and proteins replace carbohydrates as the major respiratory substrates. These results are discussed in relation to the metabolic changes observed in senescing plant tissues.
在离体玉米（Zea mays L.）根尖中研究了葡萄糖饥饿对脂肪酸氧化的影响。葡萄糖饥饿24小时后，根尖将棕榈酸氧化为CO₂的速率提高了2.5倍。对未饥饿根尖和饥饿24小时的根尖的粗颗粒部分中的不同酶活性进行了测试。饥饿后，β-氧化酶巴豆酸酶、羟酰基辅酶A（CoA）脱氢酶和硫解酶以及过氧化氢酶、苹果酸合酶和过氧化物酶体柠檬酸合酶的活性更高。然而，未检测到异柠檬酸裂解酶活性，因此表明乙醛酸循环不起作用。通过对CoA衍生物进行高效液相色谱分析后，以从[¹⁴C]棕榈酸形成[¹⁴C]乙酰辅酶A来测定总体β-氧化活性。在供给糖分的根尖中检测到一种活性，在饥饿的根尖中该活性增加了2至5倍。由于与未饥饿的根尖相比，饥饿根尖中酶活性的回收率仅略有提高，因此这些结果表明，在糖分饥饿期间组织中的β-氧化活性增加。这种增加可能是对脂质和蛋白质取代碳水化合物作为主要呼吸底物的情况作出反应的一个重要部分。结合在衰老植物组织中观察到的代谢变化对这些结果进行了讨论。
