[Localisation of peroxidase-isoenzyme group G1 in the cell wall of tobacco tissues]

Abstract

By vacuum infiltration of intercellular spaces of tobacco tissues it is possible to extract substances from cell walls which move freely in the walls. The peroxidases (E.C. 1.11.1.7) contained in these extracts are predominantly isoenzymes of GI (fast migrating anodic group) as was shown by discelektrophoresis of the extracts. As has been demonstrated previously GI is not present in the protoplast; therefore GI is the typical cell wall fraction of tobacco peroxidases. Different tissues of tobacco always differ in the isoenzyme pattern of GI. This pattern also changes during tissue development. We can therefore say that there exists an enzymatic differentiation of plant cell walls during development. As GI is not bound to the walls, it always appears in high amounts in crude extracts of plant material. Therefore GI is always called the soluble cytoplasmic fraction, but our investigations clearly demonstrate that GI is localized in cell walls only. Beside GI there are much smaller amounts of GIII (slow migrating cathodic group) and if present in the tissue GII (slow migrating anodic group) detectable in the infiltration fluids of intracellular spaces. GIII and GII are localized mainly in the protoplast. But they are also bound to the walls, ionically in the case of GIII and covalently in the case of GII.