Postranslational Phosphorylation of ADP-glucose Pyrophosphorylase in Wheat Seeds

FERRERO, DM; PIATTONI, CV; IGLESIAS, AA

Mar del Plata

Congreso; LI Reunión Anual de SAIB; 2015

SAIB

Many signals modify carbon metabolism during stages of seeds development. Phosphorylation is a mechanism regulating metabolism, but the knowledge about target enzymes in plants is poor and no report is available concerning a comparative study of the regulation taking place in seeds accumulating different carbon reserves. We found that ADP-glucose pyrophosphorylase (ADPGlcPPase, the key enzyme for starch synthesis) is differentially regulated by phosphorylation in wheat seeds (forming starch) respect to castor beans (storing tri-acyl-glycerides). Experiments of iron phosphopeptide enrichment showed that ADPGlcPPase becomes phosphorylated when wheat seeds reach advanced developmental stages, which is associated with an increase of its activity. To further study the effect of phosphorylation, we developed an expression system in Escherichia coli to produce small (S) and large (L) subunits of wheat ADPGlcPPase with specific activities of 0.5 U/mg (L+S) and 0.007 U/mg (S), while L showed no activity when produced alone. This system is also useful for the design of mutant (including phospho-mimic) proteinsin specific residues selected from bioinformatic and from phospho-proteomic studies. Results will be critical to understand the role played by phosphorylation of the enzyme as well as to explore the distribution of the regulatory mechanism between ADPGlcPPases from different sources.