Carlenor E, Persson B, Glaser E, Andersson B, Rydström J
Department of Biochemistry, University of Stockholm, S-106-91 Stockholm, Sweden.
Plant Physiol. 1988 Oct;88(2):303-8. doi: 10.1104/pp.88.2.303.
Mitochondria isolated from potato (Solanum tuberosum L.) tuber were investigated for the presence of a nicotinamide nucleotide transhydrogenase activity. Submitochondrial particles derived from these mitochondria by sonication catalyzed a reduction of NAD(+) or 3-acetylpyridine-NAD(+) by NADPH, which showed a maximum of about 50 to 150 nanomoles/minute.milligram protein at pH 5 to 6. The K(m) values for 3-acetylpyridine-NAD(+) and NADPH were about 24 and 55 micromolar, respectively. Intact mitochondria showed a negligible activity in the absence of detergents. However, in the presence of detergents the specific activity approached about 30% of that seen with submitochondrial particles. The potato mitochondria transhydrogenase activity was sensitive to trypsin and phenylarsine oxide, both agents that are known to inhibit the mammalian transhydrogenase. Antibodies raised against rat liver transhydrogenase crossreacted with two peptides in potato tuber mitochondrial membranes with a molecular mass of 100 to 115 kilodaltons. The observed transhydrogenase activities may be due to an unspecific activity of dehydrogenases and/or to a genuine transhydrogenase. The activity contributions by NADH dehydrogenases and transhydrogenase to the total transhydrogenase activity were investigated by determining their relative sensitivities to trypsin. It is concluded that, at high or neutral pH, the observed transhydrogenase activity in potato tuber submitochondrial particles is due to the presence of a genuine and specific high molecular weight transhydrogenase. At low pH an unspecific reaction of an NADH dehydrogenase with NADPH contributes to the total trans-hydrogenase activity.
对从马铃薯（Solanum tuberosum L.）块茎中分离出的线粒体进行了烟酰胺核苷酸转氢酶活性检测。通过超声处理从这些线粒体获得的亚线粒体颗粒催化NADPH对NAD(+)或3-乙酰吡啶-NAD(+)的还原，在pH 5至6时，其最大活性约为50至150纳摩尔/分钟·毫克蛋白。3-乙酰吡啶-NAD(+)和NADPH的K(m)值分别约为24和55微摩尔。完整的线粒体在没有去污剂的情况下活性可忽略不计。然而，在有去污剂的情况下，比活性接近亚线粒体颗粒的约30%。马铃薯线粒体转氢酶活性对胰蛋白酶和苯胂酸氧化物敏感，这两种试剂都已知可抑制哺乳动物转氢酶。针对大鼠肝脏转氢酶产生的抗体与马铃薯块茎线粒体膜中两条分子量为100至115千道尔顿的肽发生交叉反应。观察到的转氢酶活性可能是由于脱氢酶的非特异性活性和/或真正的转氢酶。通过测定它们对胰蛋白酶的相对敏感性，研究了NADH脱氢酶和转氢酶对总转氢酶活性的活性贡献。结论是，在高pH或中性pH下，马铃薯块茎亚线粒体颗粒中观察到的转氢酶活性是由于存在一种真正的、特异性的高分子量转氢酶。在低pH下，NADH脱氢酶与NADPH的非特异性反应对总转氢酶活性有贡献。
