Potassium modulates the metabolic regulation of Phytoplasma malic enxzyme

MUSSI, M. A.; SAIGO M; ALVAREZ C; DRINCOVICH, M. F.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Phytoplasmas (?Candidatus Phytoplasma?) are insect-vectoredplant-pathogens in which malic enzyme (AYWB-ME)fulfils a critical role for ATP generation. Previous results haveshown that AYWB-ME is selectively regulated by several differentmetabolites, which agrees with its metabolic proposedrole. In this work, we further characterize the kinetic behaviorof AYWB-ME in the presence of potassium as modulatorof this metabolic regulation. In the presence of potassiumAYWB-ME resulted highly activated, reaching around twoandfifteen-times of activation in the presence of 0.2 and 5mM respectively. When 2 mM ADP was added in the presenceof 5 mM potassium, an additional 10% AYWB-ME activationwas observed. Besides, 2 mM addition of ATP, in thepresence of 5 mM KCl, resulted in a negative effect overAYWB-ME activity reaching around 25% inhibition. On theother hand, the addition of 0.2 and 2 mM glutamine increasesAYWB-ME activity around 40% and 98% respectively. Inthis case, potassium superimposes the activation of glutamine,with no additive effect between these two modulators.This is the first study that shows a modulation effect producedby potassium over metabolic effectors of ME activitywhich could be relevant in vivo, considering the physiologicalroles that potassium levels fulfil in bacteria, e.g. modulatingion transport. Furthermore, phylogenetic analysis of severaldifferent MEs suggests that AYWB-ME is a member of a MEgroup, which is considered as the smallest scaffold knownfrom which other MEs may have evolved. This work suggeststhat this group of MEs may display a fine regulation despitepresenting a small structure, with a synergistic modulation bypotassium and metabolites