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7079047 
Journal Article 
A dual conformation of the post-decarboxylation intermediate is associated with distinct enzyme states in mycobacterial KGD (alpha-ketoglutarate decarboxylase) 
Wagner, T; Barilone, N; Alzari, PM; Bellinzoni, M; , 
2014 
Yes 
Biochemical Journal
ISSN: 0264-6021
EISSN: 1470-8728 
PORTLAND PRESS LTD 
LONDON 
425-434 
24171907 
WOS:000333718100006 
alpha-Ketoacid dehydrogenases are large multi-enzyme machineries that orchestrate the oxidative decarboxylation of alpha-ketoacids with the concomitant production of acyl-CoA and NADH. The first reaction, catalysed by alpha-ketoacid decarboxylases (E1 enzymes), needs a thiamine diphosphate cofactor and represents the overall rate-limiting step. Although the catalytic cycles of El from the pyruvate dehydrogenase (E1p) and branched-chain alpha-ketoacid dehydrogenase (E1b) complexes have been elucidated, little structural information is available on E1o, the first component of the a-ketoglutarate dehydrogenase complex, despite the central role of this complex at the branching point between the TCA (tricarboxylic acid) cycle and glutamate metabolism. In the present study, we provide structural evidence that MsKGD, the E1o (alpha-ketoglutarate decarboxylase) from Mycobacterium smegmatis, shows two conformations of the post-decarboxylation intermediate, each one associated with a distinct enzyme state. We also provide an overall picture of the catalytic cycle, reconstructed by either crystallographic snapshots or modelling. The results of the present study show that the conformational change leading the enzyme from the initial (early) to the late state, although not required for decarboxylation, plays an essential role in catalysis and possibly in the regulation of mycobacterial E1o.