A Molecular Switch and Proton Wire Synchronize the Active Sites in Thiamine Enzymes

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Science  29 Oct 2004:
Vol. 306, Issue 5697, pp. 872-876
DOI: 10.1126/science.1101030

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Thiamine diphosphate (ThDP) is used as a cofactor in many key metabolic enzymes. We present evidence that the ThDPs in the two active sites of the E1 (EC component of the pyruvate dehydrogenase complex communicate over a distance of 20 angstroms by reversibly shuttling a proton through an acidic tunnel in the protein. This “proton wire” permits the co-factors to serve reciprocally as general acid/base in catalysis and to switch the conformation of crucial active-site peptide loops. This synchronizes the progression of chemical events and can account for the oligomeric organization, conformational asymmetry, and “ping-pong” kinetic properties of E1 and other thiamine-dependent enzymes.

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