Discovery and characterization of a sulfoquinovose mutarotase using kinetic analysis at equilibrium by exchange spectroscopy
Details
Publication Year 2018-03-13, Volume 475, Issue #7, Page 1371-1383
Journal Title
Biochemistry Journal
Publication Type
Journal Article
Abstract
Bacterial sulfoglycolytic pathways catabolise sulfoquinovose (SQ), or glycosides thereof, to generate a three-carbon metabolite for primary cellular metabolism and a three-carbon sulfonate that is expelled from the cell. Sulfoglycolytic operons encoding an Embden-Meyerhof-Parnas (EMP)-like or Entner-Doudoroff (ED)-like pathway harbour an uncharacterized gene ( yihR in Escherichia coli ; PpSQ1_00415 in Pseudomonas putida ) that is upregulated in the presence of SQ and has been annotated as an aldose-1-epimerase and which may encode an SQ mutarotase. Our sequence analyses and structural modelling confirmed that these proteins possess mutarotase-like active sites with conserved catalytic residues. We over-expressed the homologue from the sulfo-ED operon of Herbaspirillumseropedicaea ( Hs SQM) and used it to demonstrate SQ mutarotase activity for the first time. This was accomplished using NMR exchange spectroscopy (EXSY), a method that allows chemical exchange of magnetization between the two SQ anomers at equilibrium. Hs SQM also catalyzed the mutarotation of various aldohexoses with an equatorial 2-hydroxy group, including D-galactose, D-glucose, D-glucose-6-phosphate, and D-glucuronic acid, but not D-mannose. Hs SQM displayed only 5-fold selectivity in terms of efficiency ( kcat/ KM) for SQ versus the glycolysis intermediate glucose-6-phosphate (Glc-6-P), however its proficiency [ kuncat / ( kcat/ KM)] for SQ was 17,000-fold better than for Glc-6-P, revealing that Hs SQM preferentially stabilises the SQ transition state.
Publisher
Portland Press
WEHI Research Division(s)
Chemical Biology
PubMed ID
29535276
Link To PubMed Central Version
https://www.ncbi.nlm.nih/pmc/articles/PMC5902678/
Open Access at Publisher's Site
https://doi.org/10.1042/BCJ20170947
Rights Notice
Refer to copyright notice on published article.


Creation Date: 2018-03-19 10:02:28
Last Modified: 2018-07-06 11:28:05
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