Structural determinants involved in the redox regulation of the Arabidopsis fumarases enzymes

MORENO, S.; TRONCONI, MA.; ZUBIMENDI, JP.; DRINCOVICH, MF.; VALACCO, P.; ANDREO CS.

Córdoba

Congreso; Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB); 2016

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Fumarase (FUM) is a homotetrameric enzyme that catalyzes the reversible hydration of fumarate to L-malate, a reaction of the tricarboxylic acid (TCA) cycle occurring in aerobic organisms. In plants, the regulation of carbon flux through of TCA cycle is especially important since mitochondrial activities have to be coordinated with photosynthesis. Arabidopsis thaliana has two FUM genes, AtFUM1 encoding the mitochondrial isoform and AtFUM2 encoding for a cytosolic one. In previous studies, we have carried out the biochemical characterization of recombinant forms of these enzymes. The emerged regulatory properties linked to AtFUM1 and -2 with the nitrogen metabolism and the cytosolic pH regulation. In this work, we have explored the redox modulation of AtFUMs, as several enzymes of TCA cycle have been reported as thiorredoxin targets in vitro. In order to identify the residues involved in the redox modulation, MALDI-TOF analysis of oxidized and reduced AtFUMs as well as site-directed mutagenesis approaches were performed. The results obtained for AtFUM1 indicated the participation of Cys219 and Cys306 in the formation of interchain disulfide bridges and suggested that Cys332, Cys389 and Cys435 are also involved in the redox regulation. Our results provide new insights into the regulatory mechanisms of FUM of plants that could link them with photosynthesis and other subcellular process.