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Solution-State 17OQuadrupole Central-Transition NMR Spectroscopy in the Active Site of Tryptophan Synthase
Ist Teil von
Angewandte Chemie, 2016-01, Vol.128 (4), p.1372
Ort / Verlag
Weinheim: Wiley Subscription Services, Inc
Erscheinungsjahr
2016
Quelle
Wiley Online Library - AutoHoldings Journals
Beschreibungen/Notizen
Oxygen is an essential participant in the acid-base chemistry that takes place within many enzyme active sites, yet has remained virtually silent as a probe in NMR spectroscopy. Here, we demonstrate the first use of solution-state 17Oquadrupole central-transition NMR spectroscopy to characterize enzymatic intermediates under conditions of active catalysis. In the 143kDa pyridoxal-5'-phosphate-dependent enzyme tryptophan synthase, reactions of the [alpha]-aminoacrylate intermediate with the nucleophiles indoline and 2-aminophenol correlate with an upfield shift of the substrate carboxylate oxygen resonances. First principles calculations suggest that the increased shieldings for these quinonoid intermediates result from the net increase in the charge density of the substrate-cofactor π-bonding network, particularly at the adjacent [alpha]-carbon site.