Linamarase and other β-glucosidases are present in the cell walls of Trifolium repens L. leaves.
Linamarase (EC 3.2.1.21) is a specialized β-glucosidase that hydrolyses the cyanogenic glucoside linamarin. Two clones of Trifolium repens L. derived from natural populations, of which one clone exhibited linamarase activity, were used in a comparative study to try to establish the localization of linamarase and other β-glucosidases. Two methods were used: the first one was vacuum infiltration of intact leaf cells, followed by centrifugation. A significant amount of linamarase and β-glucosidase activity could be extracted from intact tissue by a 0.25 M NaCl solution, indicating that these activities are localized in the apoplast. The second method, immuno-cytofluorescense of microtome sections, confirmed this. It was found that linamarase and other β-glucosidases are present in the cell walls, especially those of the epidermal cells, and in the cuticle. However their presence in the cell walls of other tissues i.e. walls of the vessels, could not be excluded. No difference in distribution could be detected between linamarase and other β-glucosidases.
Vakgroep Genetica, Universiteit van Amsterdam, Kruislaan 318, NL-1098 SM, Amsterdam, The Netherlands.
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