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Stereostructural Elucidation of Glucose Phosphorylation by Raman Optical Activity
journal contribution
posted on 2019-08-05, 20:44 authored by Yuxuan Tang, Feng Cheng, Zhaochi Feng, Guoqing Jia, Can LiPhosphorylation of
glucose is the prime step in sugar metabolism
and energy storage. Two key glucose phosphates are involved, that
is, glucose 6-phosphate (G6P) and α-glucose 1-phosphate (αG1P).
The chiral conformation of glucose, G6P, and αG1P plays an essential
role in enzyme-mediated conversions. However, few techniques were
able to give a direct view of the conformational changes from glucose
to G6P and αG1P. Here, Raman optical activity (ROA) was used
to elucidate the stereochemical evolution of glucose upon phosphorylation.
ROA was found to be extremely sensitive to different phosphorylation
sites. A characteristic ROA marker of (+)980 cm–1, originated from the phosphate group symmetric stretching vibration,
is observed for αG1P with phosphorylation at chiral C1, while
no corresponding ROA signal for G6P with phosphorylation at achiral
C6 is observed. Phosphorylation-induced gauch–gauch (gg)/gauch–trans
(gt) rotamer distribution changes can be sensitively probed by the
sign of the ROA band around 1460 cm–1. A positive
ROA band at 1465 cm–1 of glucose corresponds to
a higher gt ratio, while a negative band at 1455 cm–1 of G6P suggests a dominant gg population, and the disappearance
of this ROA band for αG1P indicates a nearly balanced gg/gt
distribution. Meanwhile, the phosphorylation at C6 and C1 could cause
dramatic reduction of the conformational flexibility of the adjacent
C4–OH and C2–OH, respectively. These stereochemical
changes revealed by ROA spectra offer a structural basis on the understanding
of sugar phosphorylation from the perspective of chirality.