13C NMR study of the generation of C2- and C3-deuterated lactic acid by tumoral pancreatic islet cells exposed to D-[1-13C]-, D-[2-13C]- and D-[6-13C]-glucose in 2H2O.
Tumoral pancreatic islet cells of the RIN5mF line were incubated for 120 min in media prepared in 2H2O and containing D-[1-13C]glucose, D-[2-13C]glucose, and D-[6-13C]glucose. The generation of C2- and C3-deuterated lactic acid was assessed by 13C NMR. The interpretation of experimental results suggests that a) the efficiency of deuteration on the C1 of D-fructose 6-phosphate does not exceed about 47% and 4% in the phosphoglucoisomerase and phosphomannoisomerase reactions, respectively; b) approximately 38% of the molecules of D-glyceraldehyde 3-phosphate generated from D-glucose escape deuteration in the sequence of reactions catalyzed by triose phosphate isomerase and aldolase; and c) about 41% of the molecules of pyruvate generated by glycolysis are immediately converted to lactate, the remaining 59% of pyruvate molecules undergoing first a single or double back-and-forth interconversion with L-alanine. It is proposed that this methodological approach, based on high resolution 13C NMR spectroscopy, may provide novel information on the regulation of back-and-forth interconversion of glycolytic intermediates in intact cells as modulated, for instance, by enzyme-to-enzyme tunneling.
Willem
R
R
High Resolution NMR Center, Faculty of Engineering, Free University of Brussels, Belgium.
Biesemans
M
M
Kayser
F
F
Malaisse
W J
WJ
D002247:Carbon Isotopes; D002478:Cells, Cultured; D003903:Deuterium; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D009682:Magnetic Resonance Spectroscopy; D014867:Water
D002247:Carbon Isotopes; D007773:Lactates; D014867:Water; D019344:Lactic Acid; D003903:Deuterium; D005947:Glucose