Ca2+-independent effects of spermine on pyruvate dehydrogenase complex activity in energized rat liver mitochondria incubated in the absence of exogenous Ca2+ and Mg2 +
Ca2+-independent effects of spermine on pyruvate dehydrogenase complex activity in energized rat liver mitochondria incubated in the absence of exogenous Ca2+ and Mg2 +
复制标题
DOI：
10.1007/s00726-008-0099-5
复制
发表时间：
2009-03-01
期刊：
影响因子：
3.5
通讯作者：
Toninello, A.
中科院分区：
文献类型：
--
作者：
Pezzato, E.;Battaglia, V.;Toninello, A.
在缺乏外源性Ca ~（2+）和Mg ~（2+）和EGTA存在的情况下，多胺精胺能刺激大鼠肝线粒体（RLM）丙酮酸脱氢酶复合物（PDC）的活性。这种刺激表现出逐渐的浓度依赖性趋势，在孵育30分钟后，在0.5 mM浓度下达到最大值，约为140%。在浓度高于0.5 mM时，精胺仍然刺激PDC，与对照相比，但显示出轻微的剂量依赖性降低。PDC刺激的变化非常接近PDC的E-1 α亚基的磷酸化水平，其调节复合物的活性，但它也是精胺的靶点。换句话说，进行性去磷酸化逐渐增强RLM的刺激和进行性磷酸化略有降低it. These结果提供了第一个证据表明，当在RLM运输，精胺可以以各种方式与PDC相互作用，表现出剂量依赖性行为。这种相互作用很可能直接发生在PDC的一种调节酶，即丙酮酸脱氢酶磷酸酶（PDP）上精胺的特定位点上。精胺与PDC的相互作用还可能涉及另一种调节酶丙酮酸脱氢酶激酶（PDK）的激活，导致E-1 α磷酸化的增加，从而降低在高多胺浓度下对PDC的刺激。从PDP和PDK同工酶活性的不同，讨论了精胺对RLM的不同影响。这表明，多胺在低浓度下刺激同工酶PDP 2，在高浓度下刺激PDK 2。
In the absence of exogenous Ca2+ and Mg2+ and in the presence of EGTA, which favours the release of endogenous Ca2+, the polyamine spermine is able to stimulate the activity of pyruvate dehydrogenase complex (PDC) of energized rat liver mitochondria (RLM). This stimulation exhibits a gradual concentration-dependent trend, which is maximum, about 140%, at 0.5 mM concentration, after 30 min of incubation. At concentrations higher than 0.5 mM, spermine still stimulates PDC, when compared with the control, but shows a slight dose-dependent decrease. Changes in PDC stimulation are very close to the phosphorylation level of the E-1 alpha subunit of PDC, which regulates the activity of the complex, but it is also the target of spermine. In other words, progressive dephosphorylation gradually enhances the stimulation of RLM and progressive phosphorylation slightly decreases it. These results provide the first evidence that, when transported in RLM, spermine can interact in various ways with PDC, showing dose-dependent behaviour. The interaction most probably takes place directly on a specific site for spermine on one of the regulatory enzymes of PDC, i.e. pyruvate dehydrogenase phosphatase (PDP). The interaction of spermine with PDC may also involve activation of another regulatory enzyme, pyruvate dehydrogenase kinase (PDK), resulting in an increase in E-1 alpha phosphorylation and consequently reduced stimulation of PDC at high polyamine concentrations. The different effects of spermine in RLM are discussed, considering the different activities of PDP and PDK isoenzymes. It is suggested that the polyamine at low concentrations stimulates the isoenzyme PDP2 and at high concentrations it stimulates PDK2.