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Evidence of Diradicals Involved in the Yeast Transketolase Catalyzed Keto‐Transferring Reactions
Author(s) -
Hsu NingShian,
Wang YungLin,
Lin KuanHung,
Chang ChiFon,
Ke ShyueChu,
Lyu SyueYi,
Hsu LiJen,
Li YiShan,
Chen ShengChia,
Wang KueiChen,
Li TsungLin
Publication year - 2018
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201800378
Subject(s) - chemistry , transketolase , diradical , stereochemistry , cofactor , electron paramagnetic resonance , catalysis , heterolysis , reaction mechanism , bond cleavage , electron transfer , reaction intermediate , photochemistry , enzyme , organic chemistry , singlet state , excited state , physics , nuclear magnetic resonance , nuclear physics
Transketolase (TK) catalyzes a reversible transfer of a two‐carbon (C 2 ) unit between phosphoketose donors and phosphoaldose acceptors, for which the group‐transfer reaction that follows a one‐ or two‐electron mechanism and the force that breaks the C2“−C3” bond of the ketose donors remain unresolved. Herein, we report ultrahigh‐resolution crystal structures of a TK (TKps) from Pichia stipitis in previously undiscovered intermediate states and support a diradical mechanism for a reversible group‐transfer reaction. In conjunction with MS, NMR spectroscopy, EPR and computational analyses, it is concluded that the enzyme‐catalyzed non‐Kekulé diradical cofactor brings about the C2“−C3” bond cleavage/formation for the C 2 ‐unit transfer reaction, for which suppression of activation energy and activation and destabilization of enzymatic intermediates are facilitated.