DEHYDROGENASES OF THE PENTOSE-PHOSPHATE PATHWAY IN RAT-LIVER PEROXISOMES
DEHYDROGENASES OF THE PENTOSE-PHOSPHATE PATHWAY IN RAT-LIVER PEROXISOMES
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DOI：
10.1111/j.1432-1033.1989.tb14898.x
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发表时间：
1989-07-15
期刊：
影响因子：
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通讯作者：
ANTONENKOV, VD
中科院分区：
文献类型：
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作者：
ANTONENKOV, VD
采用差速离心和等密度离心法研究了大鼠肝脏戊糖-磷酸循环酶的亚细胞分布。在纯化的过氧化物酶体部分以及在胞质溶胶中检测到戊糖-磷酸途径的NADP+依赖性脱氢酶（葡萄糖-6-磷酸脱氢酶和磷酸葡萄糖酸脱氢酶）的活性。两种酶均定位于过氧化物酶体基质中。长期施用降血脂药物氯贝特（乙基-α-对氯苯氧基异丁酸酯）引起纯化过氧化物酶体中葡萄糖-6-磷酸和磷酸葡萄糖酸脱氢酶的量增加1.5-2.5倍。氯贝特降低磷酸葡萄糖酸脱氢酶，但不改变葡萄糖-6-磷酸脱氢酶的活性在胞质组分。所获得的结果表明，戊糖循环的非氧化部分（转酮醇酶，转醛醇酶，丙糖磷酸异构酶和葡萄糖磷酸异构酶）的酶只存在于可溶性形式的细胞质中，但不是在过氧化物酶体或其他颗粒，并与线粒体和其他膜的酶的离子化相互作用发生在0.25 M蔗糖的组织匀浆。与过氧化氢酶类似，葡萄糖-6-磷酸脱氢酶和磷酸葡萄糖酸脱氢酶以潜伏形式存在于完整的过氧化物酶体中。这些酶对于其底物的Km值在毫摩尔范围内（葡萄糖-6-磷酸为0.2mM，6-磷酸葡萄糖酸为0.10- 0.12mM）。NADP+，而不是NAD+，作为两种酶的辅酶。葡萄糖-6-磷酸脱氢酶抑制棕榈酰辅酶A，并在较小程度上由NADPH。过氧化物酶体葡萄糖-6-磷酸和磷酸葡萄糖酸脱氢酶的分子量分别为280 kDa和96 kDa。戊糖磷酸循环酶在大鼠肝过氧化物酶体的假定功能作用进行了讨论。
Subcellular distribution of pentose-phosphate cycle enzymes in rat liver was investigated, using differential and isopycnic centrifugation. The activities of the NADP+-dependent dehydrogenases of the pentose-phosphate pathway (glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase) were detected in the purified peroxisomal fraction as well as in the cytosol. Both dehydrogenases were localized in the peroxisomal matrix. Chronic administration of the hypolipidemic drug clofibrate (ethyl-.alpha.-p-chlorophenoxyisobutyrate) caused a 1.5-2.5-fold increase in the amount of glucose-6-phosphate and phosphogluconate dehydrogenases in the purified peroxisomes. Clofibrate decreased of phosphogluconate dehydrogenase, but did not alter glucose-6-phosphate dehydrogenase activity in the cytosolic fraction. The results obtained indicate that the enzymes of the non-oxidative segment of the pentose cycle (transketolase, transaldolase, triosephosphate isomerase and glucose-phosphate isomerase) are present only in a soluble form in the cytosol, but not in the peroxisomes or other particles, and that ionogenic interaction of the enzymes with the mitochondrial and other membranes takes place during homogenization of the tissue in 0.25 M sucrose. Similar to catalase, glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase are present in the intact peroxisomes in a latent form. The enzymes have Km values for their substrates in the millimolar range (0.2 mM for glucose-6-phosphate and 0.10-0.12 mM for 6-phosphogluconate). NADP+, but not NAD+, serves as a coenzyme for both enzymes. Glucose-6-phosphate dehydrogenase was inhibited by palmitoyl-CoA, and to a lesser extent by NADPH. Peroxisomal glucose-6-phosphate and phosphogluconate dehydrogenases have molecular mass of 280 kDa and 96 kDa, respectively. The putative functional role of pentose-phosphate cycle dehydrogenases in rat liver peroxisomes is discussed.