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Structural and Functional Evolution of Isopropylmalate Dehydrogenases in the Leucine and Glucosinolate Pathways
Author(s) -
Balogun Sherifat F.,
Galant Ashley,
Jez Joseph M.
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.576.2
Subject(s) - biochemistry , arabidopsis , arabidopsis thaliana , mutagenesis , active site , glucosinolate , enzyme , amino acid , leucine , chemistry , biology , myrosinase , gene , mutation , mutant , botany , brassica
Glucosinolates are sulfur‐containing molecules produced as either defense compounds or chemical attractants in the Brassicales order of plants, which includes Arabidopsis thaliana . In humans, some of these molecules function as cancer‐prevention agents because of their ability to promote apoptosis and induce detoxification enzymes. Although the oxidative decarboxylation catalyzed by isopropylmalate dehydrogenase (IPMDH) is needed for the synthesis of leucine and glucosinolates, little is known about this family of enzymes in plants. To provide structural insight on the differential function of IPMDH, three Arabidopsis IPMDH isoforms were expressed and purified for protein crystallization. To date, crystals of AtIPMDH2 and AtIPMDH3 have been obtained. Importantly, the 2.25‐Å resolution structure of AtIPMDH2 was solved by molecular replacement and is the first detailed molecular architecture of a plant IPMDH. Through substrate modeling and site‐directed mutagenesis of AtIPMDH2, the molecular basis for the glucosinolate chain‐elongation activity of AtIPMDH1 is derived from the variation of a single amino acid in the active site. Future work will include crystallization of AtIPMDH2 with its substrates and further mutagenesis of the key residues in the active site to better understand how this enzyme catalyzes the decarboxylative formation of glucosinolates and leucine.