The Mesomeric Effect of Thiazolium on non-Kekule Diradicals in Pichia stipitis Transketolase.Hsu, N.S., Wang, Y.L., Lin, K.H., Chang, C.F., Lyu, S.Y., Hsu, L.J., Liu, Y.C., Chang, C.Y., Wu, C.J., Li, T.L.
(2018) Angew Chem Int Ed Engl 57: 1802-1807
- PubMed: 29243887
- DOI: 10.1002/anie.201709799
- Primary Citation of Related Structures:
5XSM, 5XSA, 5XSB, 5XRY, 5XS6, 5XTL, 5XUF, 5XTV, 5XVT
- PubMed Abstract:
It is theoretically plausible that thiazolium mesomerizes to congeners other than carbene in a low effective dielectric binding site; especially given the energetics and uneven electronegativity of carbene groups. However, such a phenomenon has never ...
It is theoretically plausible that thiazolium mesomerizes to congeners other than carbene in a low effective dielectric binding site; especially given the energetics and uneven electronegativity of carbene groups. However, such a phenomenon has never been reported. Nine crystal structures of transketolase obtained from Pichia stipitis (TKps) are reported with subatomic resolution, where thiazolium displays an extraordinary ring-bending effect. The bent thiazolium congeners correlate with non-Kekulé diradicals because there is no gain or loss of electrons. In conjunction with biophysical and biochemical analyses, it is concluded that ring bending is a result of tautomerization of thiazolium with its non- Kekulé diradicals, exclusively in the binding site of TKps. The chemophysical properties of these thiazolium mesomers may account for the great variety of reactivities carried out by thiamine-diphosphate-containing (ThDP) enzymes. The stability of ThDP in living systems can be regulated by the levels of substrates, and hydration and dehydration, as well as diradical-mediated oxidative degradation.
Biotechnology Center, National Chung Hsing University, Taichung City, 402, Taiwan.