Biochemistry

Abstract

CS-11-5 - Structure and mechanism of isopropylmalate dehydrogenase from Arabdiopsis thaliana: insights on leucine and aliphatic glucosinolate biosynthesis

Monday, July 16
2:23 PM - 2:43 PM

Isopropylmalate dehydrogenase (IPMDH) and 3-(2-methyl-thio)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 Mg2+ 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 Lys232 activates a water molecule for catalysis.  Structural analysis of the AtIPMDH2 K232M mutant and isothermal titration calorimetry supports a key role of Lys232 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.


 

Co-Authors

Ronald Nwumeh – Washington University; Joseph Jez, Ph.D. – Washington University

Soon Goo Lee

Postdoctoral Associate
Washington University in St. Louis

Presentation(s):

Send Email for Soon Goo Lee


Assets

CS-11-5 - Structure and mechanism of isopropylmalate dehydrogenase from Arabdiopsis thaliana: insights on leucine and aliphatic glucosinolate biosynthesis



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Structure and mechanism of isopropylmalate dehydrogenase from Arabdiopsis thaliana: insights on leucine and aliphatic glucosinolate biosynthesis