Inhibition and uncoupling of photophosphorylation in isolated chloroplasts by organotin, organomercury and diphenyleneiodonium compounds.
Inhibition and uncoupling of photophosphorylation in isolated chloroplasts by organotin, organomercury and diphenyleneiodonium compounds.
复制标题
有机锡、有机汞和二亚苯基碘化合物对分离叶绿体中光磷酸化的抑制和解偶联。
作者：
Angela S. Watling;M. Selwyn
1.三烷基锡、三苯基锡和二苯基碘化合物在磷酸盐或砷盐存在下抑制ADP刺激的豌豆叶绿体释放O(2)。三丁基锡和三苯基锡是最有效的抑制剂，这表明作用部位具有高度疏水性。苯基汞对光磷酸化的抑制作用很差，这表明硫醇基团不参与。2.在含氯(-)的介质中，三乙基锡是叶绿体光合磷酸化的解偶联剂，但在阴离子-氢氧化物交换中不活跃的NO(3)(-)或SO(4)(2-)取代Cl(-)时，三乙基锡的解偶联活性很小。结果表明，三乙基锡的解偶联是氯(-)-羟基(-)交换和氯(-)的天然结合的结果。三丁基锡、三苯基锡和苯基醋酸汞的解偶联活性较低，可能是因为这些化合物的解偶联活性部分被抑制作用所掩盖。3.高浓度时，有机锡化合物对氰化物、间氯苯肼或NH(4)Cl解偶联的电子传递有抑制作用。在这些高浓度下，有机锡化合物可能会产生类似洗涤剂的膜结构紊乱。相反，二苯碘硫酸盐在低浓度时抑制解偶联的电子传递，但这种抑制程度小于对光磷酸化的抑制，这表明该化合物也抑制了磷酸化反应和电子传递。4.这些化合物对基础电子传递的影响是复杂的，并且与反应介质的pH有关。然而，它们可以用三种作用来解释：抑制磷酸化反应、解偶联和直接抑制电子传递。5.二苯碘硫酸盐对吩嗪甲硫酸盐诱导的细胞周期光磷酸化的抑制作用表明，它抑制光系统1的区域。
1. Trialkyltin, triphenyltin and diphenyleneiodonium compounds inhibited ADP-stimulated O(2) evolution by isolated pea chloroplasts in the presence of phosphate or arsenate. Tributyltin and triphenyltin were the most effective inhibitors, which suggests a highly hydrophobic site of action. Phenylmercuric acetate was a poor inhibitor of photophosphorylation, which suggests that thiol groups are not involved. 2. Triethyltin was a potent uncoupler of photophosphorylation by isolated chloroplasts in media containing Cl(-), but had little uncoupling activity when Cl(-) was replaced by NO(3) (-) or SO(4) (2-), which are inactive in the anion-hydroxide exchange. It is suggested that uncoupling by triethyltin is a result of the Cl(-)-OH(-) exchange together with a natural uniport of Cl(-). Tributyltin, triphenyltin and phenylmercuric acetate had low uncoupling activity, probably because in these compounds the uncoupling activity is partially masked by inhibitory effects. 3. At high concentrations the organotin compounds caused inhibition of electron transport uncoupled by carbonyl cyanide m-chlorophenylhydrazone or NH(4)Cl. At these high concentrations the organotin compounds may be producing a detergent-like disorganization of the membrane structure. In contrast, diphenyleneiodonium sulphate inhibited uncoupled electron transport at low concentrations; however, this inhibition is less than the inhibition of photophosphorylation, which suggests that the compound also inhibits the phosphorylation reactions as well as electron transport. 4. The effects of these compounds on basal electron transport were complex and depended on the pH of the reaction media. However, they can be explained on the basis of three actions: inhibition of the phosphorylation reactions, uncoupling and direct inhibition of electron transport. 5. The inhibition of cyclic photophosphorylation in the presence of phenazine methosulphate by diphenyleneiodonium sulphate shows that it inhibits in the region of photosystem 1.