IAL   21557
INSTITUTO DE AGROBIOTECNOLOGIA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
On the in vitro phosphorylation of aldose-6-phosphate reductase from apple and peach leaves
Autor/es:
CARLOS M. FIGUEROA; CLAUDIA V. PIATTONI; ALBERTO A. IGLESIAS
Lugar:
Montréal, Canadá
Reunión:
Congreso; Plant Biology 2010; 2010
Institución organizadora:
American Society of Plant Biologists and Canadian Society of Plant Physiologists
Resumen:
In addition to sucrose and starch, many plant
species synthesize glucitol (Gol) as a main photosynthetic product. Gol
synthesis occurs by the action of a NADPH-dependent aldose-6-phosphate
reductase (A6PRase, EC 1.1.1.200), which converts glucose-6P (Glc6P) into
Gol6P, followed by the hydrolysis of the phosphate group by a specific
phosphatase. Gol is then transferred to sink tissues, where it can be converted
into fructose by a NAD-dependent Gol dehydrogenase. Despite the importance of
these enzymes for carbon partitioning in plants from the Rosaceae family (i.e.,
apple and peach), few studies deal with their characterization. In this work,
we show the recombinant expression, one-step purification and kinetic
characterization of A6PRase from apple and peach leaves. The purified enzymes
exhibited kinetic properties similar to those reported for A6PRase purified
from the leaves of apple and loquat. Utilizing [32P]ATP, we found
that the recombinant enzymes can be in vitro phosphorylated by extracts
from leaves of the two plant species. Using A6PRase as a substrate, a Mg2+-
and Ca2+-dependent protein kinase (PKase) was partially purified
from apple and peach leaves. In our hands, the PKase was inhibited by
ribose-5P, PPi, phosphoenolpyruvate, fructose-1,6bisP, Gol6P and Glc6P. As intracellular
levels of these metabolites fluctuate along the day, it is proposed that the
PKase could be regulated with dependence on the day/night cycle. Considering
that the activity of A6PRase was found to change during the photoperiod, it is
tempting to speculate that the enzyme could be light/dark modulated in vivo
through protein phosphorylation.