A specific association between the glyoxylic-acid-cycle enzymes isocitrate lyase and malate synthase

There is accumulating evidence that metabolic pathways are organized in vivo as multienzyme clusters or metabolons. To assess interactions between consecutive enzymes of a pathway in vitro, it is usually essential to modify the physical properties of water around the enzymes, e.g. by immobilizing the latter onto a solid support. Such immobilized enzyme preparations can be embedded in agarose gels and used for affinity electrophoresis [Beeckmans, S., Van Driessche, E. & Kanarek, L. (1989) Eur. J. Biochem. 183, 449-454; Beeckmans, S., Van Driessche, E. & Kanarek, L. (1990) J. Cell. Biochem. 43, 297-306]. In this study we use the aforementioned technique to investigate the association between two plant glyoxylic acid cycle enzymes, i.e. isocitrate lyase and malate synthase. A specific histochemical staining technique is described for both enzymes. Affinity electrophoresis using either isocitrate lyase or malate synthase as the immobilized enzyme clearly shows that associations are formed between both enzymes. Moreover, experiments with metabolically unrelated enzymes prove that the observed interaction is specific.