[Compartmentation and properties of the MDH-isoenzymes from watermelon cotyledons (Citrullus vulgaris Schrad.)].
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).
Institut für Allgemeine Botanik Arbeitsgruppe Biochemie der Morphogenese, Ruhr-Universität, D-4630, Bochum-Querenburg, Federal Republic of Germany.
B
B
Hock