Institute for Photobiology of Cells and Organelles, Brandeis University, Waltham, Massachusetts 02254.
Plant Physiol. 1992 Sep;100(1):327-33. doi: 10.1104/pp.100.1.327.
The role of an electron transport pathway associated with aerobic carbohydrate degradation in isolated, intact chloroplasts was evaluated. This was accomplished by monitoring the evolution of (14)CO(2) from darkened spinach (Spinacia oleracea) and Chlamydomonas reinhardtii chloroplasts externally supplied with [(14)C]fructose and [(14)C]glucose, respectively, in the presence of nitrite, oxaloacetate, and conventional electron transport inhibitors. Addition of nitrite or oxaloacetate increased the release of (14)CO(2), but it was shown that O(2) continued to function as a terminal electron acceptor. (14)CO(2) evolution was inhibited up to 30 and 15% in Chlamydomonas and spinach, respectively, by 50 mum rotenone and by amytal, but at 500- to 1000-fold higher concentrations, indicating the involvement of a reduced nicotinamide adenine dinucleotide phosphate-plastoquinone oxidoreductase. (14)CO(2) release from the spinach chloroplast was inhibited 80% by 25 mum 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone. (14)CO(2) release was sensitive to propylgallate, exhibiting approximately 50% inhibition in Chlamydomonas and in spinach chloroplasts of 100 and 250 mum concentrations, respectively. These concentrations were 20- to 50-fold lower than the concentrations of salicylhydroxamic acid (SHAM) required to produce an equivalent sensitivity. Antimycin A (100 mum) inhibited approximately 80 to 90% of (14)CO(2) release from both types of chloroplast. At 75 mum, sodium azide inhibited (14)CO(2) evolution about 50% in Chlamydomonas and 30% in spinach. Sodium azide (100 mm) combined with antimycin A (100 mum) inhibited (14)CO(2) evolution more than 90%. (14)CO(2) release was unaffected by uncouplers. These results are interpreted as evidence for a respiratory electron transport pathway functioning in the darkened, isolated chloroplast. Chloroplast respiration defined as (14)CO(2) release from externally supplied [1-(14)C]glucose can account for at least 10% of the total respiratory capacity (endogenous release of CO(2)) of the Chlamydomonas reinhardtii cell.
评估了与有氧碳水化合物降解相关的电子传递途径在分离完整叶绿体中的作用。这是通过监测黑暗处理的菠菜（Spinacia oleracea）和莱茵衣藻（Chlamydomonas reinhardtii）叶绿体中（14）CO 2 的演化来实现的，这些叶绿体分别以外源提供的[（14）C]果糖和[（14）C]葡萄糖为底物，并在亚硝酸盐、草酰乙酸和传统电子传递抑制剂的存在下进行。添加亚硝酸盐或草酰乙酸会增加（14）CO 2 的释放，但事实证明 O 2 仍然是末端电子受体。（14）CO 2 的释放分别在莱茵衣藻和菠菜中被 50μm 鱼藤酮和阿米替林抑制了 30%和 15%，但在 500-1000 倍更高的浓度下，表明涉及还原型烟酰胺腺嘌呤二核苷酸磷酸-质体醌氧化还原酶。菠菜叶绿体中（14）CO 2 的释放被 25μm 2,5-二溴-3-甲基-6-异丙基对苯醌抑制了 80%。（14）CO 2 的释放对丙基没食子酸敏感，在莱茵衣藻和菠菜叶绿体中分别有大约 50%的抑制，浓度分别为 100 和 250μm。这些浓度比水杨羟肟酸（SHAM）所需的浓度低 20-50 倍，以产生相同的敏感性。抗霉素 A（100μm）抑制了两种类型叶绿体中（14）CO 2 释放的约 80-90%。在 75μm 时，叠氮化钠抑制了莱茵衣藻中（14）CO 2 演化约 50%，而在菠菜中则抑制了 30%。叠氮化钠（100mM）与抗霉素 A（100μm）联合使用抑制了（14）CO 2 释放超过 90%。（14）CO 2 的释放不受解偶联剂的影响。这些结果被解释为在黑暗、分离的叶绿体中存在呼吸电子传递途径的证据。定义为从外部供应的[1-（14）C]葡萄糖中释放（14）CO 2 的叶绿体呼吸可以占莱茵衣藻细胞总呼吸能力（内源 CO 2 释放）的至少 10%。
