Swiezewska E, Dallner G, Andersson B, Ernster L
Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, University of Stockholm, Sweden.
J Biol Chem. 1993 Jan 15;268(2):1494-9.
The localization of ubiquinone (UQ) and plastoquinone (PQ) biosynthesis in subfractions isolated from spinach leaves has been studied. UQ-9 and UQ-10 were found mainly in mitochondria, whereas PQ was enriched in chloroplasts, but also found in Golgi membranes. alpha-Unsaturated polyprenol-11 was also present at a low concentration in chloroplasts. Autoradiography revealed the presence of nonaprenyl-4-hydroxybenzoate (NPHB) and nonaprenyl-2-methylquinol (NPMQ) transferase activities involved in quinone biosynthesis in all subfractions, but the specific activities involved in quinone biosynthesis in the total microsomal fraction were 20 times higher than those in mitochondria and chloroplasts. The isolated Golgi vesicles were particularly enriched in both activities. When the incubation medium containing total microsomes or Golgi membranes was supplemented with NADH, NADPH, S-adenosylmethionine, and an ATP-generating system, NPHB and NPMQ were transferred to UQ-9 and PQ, respectively. trans-Prenyltransferase, which synthesizes the side chain of UQ and PQ, was present in the total microsomal fraction. With farnesyl-PP as substrate, no product was formed, but with geranyl-PP, solanesyl-PP was synthesized and transferred to 4-hydroxybenzoate present in the total microsomal fraction. The results show that these membranes from spinach contain farnesyl-PP synthetase. It is concluded that the plant leaf Golgi membranes contain the enzymes for both UQ and PQ biosynthesis and that a specific transport and targeting system is required for selective transfer of UQ to the mitochondria and of PQ to the chloroplast.
对从菠菜叶片中分离出的亚组分中泛醌（UQ）和质体醌（PQ）生物合成的定位进行了研究。发现UQ - 9和UQ - 10主要存在于线粒体中，而PQ在叶绿体中含量丰富，但在高尔基体膜中也有发现。α - 不饱和聚戊烯醇 - 11在叶绿体中的浓度也较低。放射自显影显示，所有亚组分中均存在参与醌生物合成的壬基 - 4 - 羟基苯甲酸（NPHB）和壬基 - 2 - 甲基对苯二酚（NPMQ）转移酶活性，但总微粒体组分中参与醌生物合成的比活性比线粒体和叶绿体中的高20倍。分离出的高尔基体小泡中这两种活性尤其丰富。当向含有总微粒体或高尔基体膜的孵育培养基中添加NADH、NADPH、S - 腺苷甲硫氨酸和ATP生成系统时，NPHB和NPMQ分别转移到UQ - 9和PQ中。合成UQ和PQ侧链的反式异戊二烯基转移酶存在于总微粒体组分中。以法尼基焦磷酸（farnesyl - PP）为底物时，未形成产物，但以香叶基焦磷酸（geranyl - PP）为底物时，合成了茄尼基焦磷酸（solanesyl - PP）并转移到总微粒体组分中存在的4 - 羟基苯甲酸中。结果表明，菠菜的这些膜含有法尼基焦磷酸合成酶。得出的结论是，植物叶片高尔基体膜含有UQ和PQ生物合成的酶，并且需要特定的转运和靶向系统来将UQ选择性地转移到线粒体中，将PQ选择性地转移到叶绿体中。
