Structure and Mechanism of Isopropylmalate Dehydrogenase from Arabidopsis thaliana: INSIGHTS ON LEUCINE AND ALIPHATIC GLUCOSINOLATE BIOSYNTHESIS.
J Biol Chem
; 291(26): 13421-30, 2016 Jun 24.
Article
em En
| MEDLINE
| ID: mdl-27137927
ABSTRACT
Isopropylmalate dehydrogenase (IPMDH) and 3-(2'-methylthio)ethylmalate dehydrogenase catalyze the oxidative decarboxylation of different ß-hydroxyacids in the leucine- and methionine-derived glucosinolate biosynthesis pathways, respectively, in plants. Evolution of the glucosinolate biosynthetic enzyme from IPMDH results from a single amino acid substitution that alters substrate specificity. Here, we present the x-ray crystal structures of Arabidopsis thaliana IPMDH2 (AtIPMDH2) in complex with either isopropylmalate and Mg(2+) or NAD(+) These structures reveal conformational changes that occur upon ligand binding and provide insight on the active site of the enzyme. The x-ray structures and kinetic analysis of site-directed mutants are consistent with a chemical mechanism in which Lys-232 activates a water molecule for catalysis. Structural analysis of the AtIPMDH2 K232M mutant and isothermal titration calorimetry supports a key role of Lys-232 in the reaction mechanism. This study suggests that IPMDH-like enzymes in both leucine and glucosinolate biosynthesis pathways use a common mechanism and that members of the ß-hydroxyacid reductive decarboxylase family employ different active site features for similar reactions.
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Assunto principal:
Arabidopsis
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Proteínas de Arabidopsis
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3-Isopropilmalato Desidrogenase
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Glucosinolatos
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Leucina
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article