A multi-level regulation of Arabidopsis fumarases reveals novel emergent properties of C4 metabolism.

JUAN PABLO ZUBIMENDI; MARIA FABIANA DRINCOVICH; ANDREO, CS; MARCOS TRONCONI

Congreso; LI Reunión de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2015

Fumarase (FUM) is involved in the metabolism of C4 organic acids, catalyzing reversible hydration of fumarate to L-malate. Arabidopsis thaliana genome possesses two genes for this enzyme: FUM1, encoding for a mitochondrial isoform, and FUM2 that could generate two cytosolic polypeptides (FUM2.1 and -2.2) differing in their carboxyl terminal region due to an alternative splicing process of the primary transcript. Here, FUM1, 2.1 and -2.2 were biochemically characterized by a recombinant approach. We could establish complex regulatory mechanisms of FUMs activity that occur at the mRNA and protein level, involving changes in mRNA maturation and abundance, switching the pH medium as well as the allosteric and redox regulation. Specifically, alkaline conditions and high asparagine or glutamine concentrations stimulated the fumarate generation by FUM2. Also, FUM1 and -2 activities are stimulated by the reduction of disulfide bridges between cysteine residues located on different subunits of the tetramer. This was observed either using reducing or oxidizing agents as well as components of redox systems of Arabidopsis leaves in the presence of NADPH. Overall, these results reveal a multi-level regulation of FUM activity in A. thaliana and new emergent properties for the control of C4 metabolism can be suggested.