Preliminary studies on the inhibition of D-sorbitol-6-phosphate 2–dehydrogenase from Escherichia coli with substrate analogues

Abstract

D-Sorbitol-6-phosphate 2-dehydrogenase catalyzes the NADH-dependent conversion of D-fructose 6-phosphate to D-sorbitol 6-phosphate and improved production and purification of the enzyme from Escherichia coli is reported. Preliminary inhibition studies of the enzyme revealed 5-phospho-D-arabinonohydroxamic acid and 5-phospho-D-arabinonate as new substrate analogue inhibitors of the F6P catalyzed reduction with IC₅₀ values of (40 ± 1) μM and (48 ± 3) μM and corresponding K_m/IC₅₀ ratio values of 14 and 12, respectively. Furthermore, we report here the phosphomannose isomerase substrate D-mannose 6-phosphate as the best inhibitor of E. coli D-sorbitol-6-phosphate 2-dehydrogenase yet reported with an IC₅₀ = 7.5 ± 0.4 μM and corresponding K_m/IC₅₀ ratio = about 76.

Keywords::

• Sorbitol-6-phosphate dehydrogenase
• phosphomannose isomerase
• phosphoglucose isomerase
• inhibition
• phosphate sugars

Acknowledgements

Pr. Emile Van Schaftingen (Laboratoire de Chimie Physiologique, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, B-1200 Brussels, Belgium) is greatly acknowledged for providing us with the Escherichia coli BL21 pLysS bacteria carrying the pET3a-s6pdh plasmid and for helpful discussions during protein purification.