Dieuaide M, Couée I, Pradet A, Raymond P
INRA, Centre de Recherche de Bordeaux, Villenave d'Ornon, France.
Biochem J. 1993 Nov 15;296 ( Pt 1)(Pt 1):199-207. doi: 10.1042/bj2960199.
Fatty acid beta-oxidation was studied in organellar fractions from maize root tips by h.p.l.c. and radiometric analysis of the products of incubations with [1-14C]octanoate and [1-14C]palmitate. In crude organellar fractions containing both mitochondria and peroxisomes, octanoate and palmitate beta-oxidation, as determined by the production of acetyl-CoA, was functional and, for palmitate, was activated 4-12-fold after subjecting the root tips to 48 h of glucose starvation. The sensitivity to a 'cocktail' of respiratory-chain inhibitors containing cyanide, azide and salicylhydroxamate depended on the conditions of incubation, with no inhibition in a medium facilitating peroxisomal beta-oxidation and a significant inhibition in a medium potentially facilitating mitochondrial beta-oxidation. Indeed, preparations of highly purified mitochondria from glucose-starved root tips were able to oxidize octanoate and palmitate to give organic acids of the tricarboxylic acid cycle. This activity was inhibited 5-10-fold by the above cocktail of respiratory-chain inhibitors, with no parallel accumulation of acetyl-CoA, thus showing that the inhibition affected beta-oxidation rather than the pathway from acetyl-CoA to the organic acids. This provides the first evidence that the complete beta-oxidation pathway from fatty acids to citrate was functional in mitochondria from a higher plant. Moreover, an acyl-CoA dehydrogenase activity was shown to be present in the purified mitochondria. In contrast with the peroxisomal activity, mitochondrial beta-oxidation showed the same efficiency with octanoate and palmitate and was strictly dependent on glucose starvation.
通过高效液相色谱法（h.p.l.c.）以及对[1-14C]辛酸和[1-14C]棕榈酸孵育产物的放射性分析，研究了玉米根尖细胞器组分中的脂肪酸β-氧化作用。在含有线粒体和过氧化物酶体的粗细胞器组分中，通过乙酰辅酶A的生成来测定，辛酸和棕榈酸的β-氧化作用是有功能的，并且对于棕榈酸而言，在根尖经过48小时葡萄糖饥饿处理后，其β-氧化作用被激活了4至12倍。对含有氰化物、叠氮化物和水杨羟肟酸的呼吸链抑制剂“鸡尾酒”的敏感性取决于孵育条件，在有利于过氧化物酶体β-氧化作用的培养基中没有抑制作用，而在可能有利于线粒体β-氧化作用的培养基中有显著抑制作用。实际上，来自葡萄糖饥饿根尖的高度纯化线粒体的制剂能够将辛酸和棕榈酸氧化为三羧酸循环的有机酸。上述呼吸链抑制剂“鸡尾酒”使这种活性受到5至10倍的抑制，同时没有乙酰辅酶A的平行积累，因此表明这种抑制作用影响的是β-氧化作用而非从乙酰辅酶A到有机酸的途径。这首次证明了从脂肪酸到柠檬酸的完整β-氧化途径在高等植物的线粒体中是有功能的。此外，在纯化的线粒体中显示存在酰基辅酶A脱氢酶活性。与过氧化物酶体的活性不同，线粒体β-氧化作用对辛酸和棕榈酸表现出相同的效率，并且严格依赖于葡萄糖饥饿。
