ibclogo XVI International Botanical Congess


Abstract Number: 3895
Poster No. = 2003


SUBCELLULAR COMPARTMENTATION AND ASSAY OF L-GALACTONON-GAMMA-LACTONE DEHYDROGENASE IN POTATO LEAVES


C. Bartoli, G. Pastori and C.H. Foyer, IACR-Rothamsted, Harpenden, Herts, AL5 2JQ, UK


Ascorbate biosynthesis in plants has remained unresolved until recently, many steps remain to be elucidated. The ultimate step of the pathway involves the conversion of L-galactono-gamma-lactone (GL) to ascorbic acid, a reaction catalysed by the membrane-bound enzyme, L-galactono-lactone dehydrogenase (GLDHase). The activity of this enzyme is frequently measured by the concomitant reduction of cytomchrome C but the natural oxidising substrate in unknown. Up until now the activity of this enzyme has only been measured in purified mitochondria. A simple system for this enzyme was therefore devised. Sub-cellular fractionation experiments and Western blots revealed that 90% of the GLDHase activity was localised in the mitochondrial inner membrane, the remaining 10% being associated with the microsomal fraction.


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