CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
artículos
Título:
Allosteric substrate inhibition of Arabidopsis NAD-dependent malic enzyme 1 is released by fumarate
Autor/es:
TRONCONI, M.; GERRARD WHEELER, M.; MARTINATTO, A; ZUBIMENDI, JP; ANDREO CS; DRINCOVICH, M.F.
Revista:
PHYTOCHEMISTRY
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2015 vol. 111 p. 37 - 47
ISSN:
0031-9422
Resumen:
Plant mitochondria can use L-malate and fumarate, which accumulate in large levels, as respiratory substrates. In part, this property is due to the presence of NAD-dependent malic enzymes (NAD-ME) witparticular biochemical characteristics. Arabidopsis NAD-ME1 exhibits a non-hyperbolic behavior fothe substrate L-malate, and its activity is strongly stimulated by fumarate. Here, the possible structurconnection between these properties was explored through mutagenesis, kinetics, and fluorescence studies. The results indicated that NAD-ME1 has a regulatory site for L-malate that can also bind fumaratL-Malate binding to this site elicits a sigmoidal and low substrate-affinity response, whereas fumaratbinding turns NAD-ME1 into a hyperbolic and high substrate affinity enzyme. This effect was alsobserved when the allosteric site was either removed or altered. Hence, fumarate is not really an activator, but suppresses the inhibitory effect of L-malate. In addition, residues Arg50, Arg80 and Arg84 showedifferent roles in organic acid binding. These residues form a triad, which is the basis of the homo anheterotrophic effects that characterize NAD-ME1. The binding of L-malate and fumarate at the samallosteric site is herein reported for a malic enzyme and clearly indicates an important role of NADME1 in processes that control flow of C4 organic acids in Arabidopsis mitochondrial metabolism.