Hock B
Institut für Allgemeine Botanik Arbeitsgruppe Biochemie der Morphogenese, Ruhr-Universität, D-4630, Bochum-Querenburg, Federal Republic of Germany.
Planta. 1973 Jun;112(2):137-48. doi: 10.1007/BF00388584.
Five MDH-isoenzymes (I-V) from cotyledons of dark-grown water-melon seedlings older than 2 days can be identified by disc-electrophoresis. By isolating and fractionating cell organelles (10000 g fraction) by density gradient centrifugation (Fig. 1) the following compartmentation of the MDH-isoenzymes can be shown: the mitochondria contain isoenzyme III and the glyoxysomes preponderantly (if not exclusive) isoenzyme V (Fig. 2), whereas the isoenzymes I, II, and IV belong to the cytosol.The 5 MDH-isoenzymes differ in several properties, e.g. differential precipitation by ammonium sulfate (Fig. 4) or isoelectric point (Fig. 5). The glyoxysomal MDH is a relatively basic protein (isoelectric point at pH 8.7), whereas the isoelectric points of the other isoenzymes lie between pH 6.4 (IV) and pH 4.7 (I).
通过圆盘电泳可以鉴定出2日龄以上黑暗培养的西瓜幼苗子叶中的五种苹果酸脱氢酶同工酶（I-V）。通过密度梯度离心法分离和分级分离细胞器（10000g级分）（图1），可以显示苹果酸脱氢酶同工酶的以下区室化：线粒体含有同工酶III，乙醛酸循环体主要（如果不是唯一）含有同工酶V（图2），而同工酶I、II和IV属于细胞质。这5种苹果酸脱氢酶同工酶在几个特性上有所不同，例如硫酸铵分级沉淀（图4）或等电点（图5）。乙醛酸循环体苹果酸脱氢酶是一种相对碱性的蛋白质（等电点为pH 8.7），而其他同工酶的等电点在pH 6.4（IV）和pH 4.7（I）之间。
