Dual anomeric specificity of phosphomannoisomerase assessed by 2D phase sensitive 13C EXSY NMR.
The reversible conversion between D-mannose 6-phosphate and D-fructose 6-phosphate catalyzed by yeast phosphomannoisomerase was studied by phase sensitive 2D 13C-(1H) EXSY NMR spectroscopy at 100.623 MHz, using 13C enriched substrates in the C2 position of the D-hexose 6-phosphates. The unique pair of isomerization cross-peaks observed in the 2D EXSY map correlates the 13C2 resonances of the beta-anomers of both D-[2-13C]-mannose 6-phosphate and D-[213C]-fructose 6-phosphate. This indicates that phosphomannoisomerase specifically catalyzes the reversible conversion between beta-D-mannose 6-phosphate and beta-D-fructose 6-phosphate. Since phosphoglucoisomerase was recently found to catalyze specifically the interconversion of alpha-D-glucose 6-phosphate and beta-D-fructose 6-phosphate, the beta-anomer of the ketohexose ester could be directly channeled in a multi-enzyme system involving phosphoglucoisomerase, phosphomannoisomerase and phosphofructokinase.
Malaisse-Lagae
F
F
Laboratory of Experimental Medicine, Erasmus Medical School, Brussels Free University, Belgium.
Willem
R
R
Penders
M
M
Malaisse
W J
WJ
D005636:Fructosephosphates / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008359:Mannose-6-Phosphate Isomerase / Q000737:chemistry*; D008360:Mannosephosphates / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism
D005636:Fructosephosphates; D008360:Mannosephosphates; D009097:Multienzyme Complexes; C027693:mannose-6-phosphate; C027618:fructose-6-phosphate; D008359:Mannose-6-Phosphate Isomerase