Adenosine diphosphate glucose pyrophosphatase: a plastidial phosphodiesterase that prevents starch biosynthesis
Fecha
2000Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Impacto
|
10.1073/pnas.120168097
Resumen
A distinct phosphodiesterasic activity (EC 3.1.4) was found in both
mono- and dicotyledonous plants that catalyzes the hydrolytic
breakdown of ADPglucose (ADPG) to produce equimolar amounts
of glucose-1-phosphate and AMP. The enzyme responsible for this
activity, referred to as ADPG pyrophosphatase (AGPPase), was
purified over 1,100-fold from barley leaves and subjected to
biochemical characteriz ...
[++]
A distinct phosphodiesterasic activity (EC 3.1.4) was found in both
mono- and dicotyledonous plants that catalyzes the hydrolytic
breakdown of ADPglucose (ADPG) to produce equimolar amounts
of glucose-1-phosphate and AMP. The enzyme responsible for this
activity, referred to as ADPG pyrophosphatase (AGPPase), was
purified over 1,100-fold from barley leaves and subjected to
biochemical characterization. The calculated Keq* (modified equilibrium
constant) value for the ADPG hydrolytic reaction at pH 7.0
and 25°C is 110, and its standard-state free-energy change value
(DG*) is 22.9 kcalymol (1 kcal 5 4.18 kJ). Kinetic analyses showed
that, although AGPPase can hydrolyze several low-molecular
weight phosphodiester bond-containing compounds, ADPG
proved to be the best substrate (Km 5 0.5 mM). Pi and phosphorylated
compounds such as 3-phosphoglycerate, PPi, ATP, ADP,
NADP1, and AMP are inhibitors of AGPPase. Subcellular localization
studies revealed that AGPPase is localized exclusively in the
plastidial compartment of cultured cells of sycamore (Acer pseudoplatanus
L.), whereas it occurs both inside and outside the
plastid in barley endosperm. In this paper, evidence is presented
that shows that AGPPase, whose activity declines concomitantly
with the accumulation of starch during development of sink
organs, competes with starch synthase (ADPG:1,4-a-D-glucan 4-a-
D-glucosyltransferase; EC 2.4.1.21) for ADPG, thus markedly blocking
the starch biosynthesis. [--]
Materias
ADPG pyrophosphatase,
Phosphodiesterase,
Starch biosynthesis
Editor
National Academy of Sciences
Publicado en
PNAS July 18, 2000 97 (15) 8705-8710
Departamento
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua