In vitro formation of glucose 6-phosphate from 3-phosphoglycerate by rat liver cytosol.
Liver cytosol preparations from 48 h starved rats, supplemented with 3 mM ATP, 0.5 mM sn-glycerol 3-phosphate, 10mM MgSO4 and a NADH-regenerating system showed a net glucose 6-phosphate formation from 2mM 3-phosphoglycerate of 0.72 micromol x min-1 x (g liver)-1. Glycerol 3-phosphate slightly increased when added at 0.5 mM; in its absence, dihydroxyacetone-phosphate formed from 3-phosphoglycerate was mainly reduced to glycerol 3-phosphate at the expense of fructose 1,6-bisphosphate and glucose 6-phosphate synthesis; when glycerol 3-phosphate was added at higher concentrations, net utilization occurred. The rate of glucose 6-phosphate formation positively correlated with the concentration of 3-phosphoglycerate and with the ratio of ATP/ADP. Increasing NADH concentrations stimulated the flow from 3-phosphoglycerate to glyceraldehyde 3-phosphate but also enhanced the reduction of dihydroxyacetone phosphate to glycerol 3-phosphate; as a result, the concentration of free NADH had little effect on the rate of glucose 6-phosphate formation. Lowering the concentration of magnesium from 10mM to 4mM, corresponding to free Mg2 concentrations of 7 and 0.6 mM respectively, resulted in a 30% increase of the rate of glucose 6-phosphate formation. The physiological relevance of the results presented is discussed.
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D003600:Cytosol / Q000378:metabolism; D005958:Glucosephosphates / Q000096:biosynthesis*; D005994:Glycerophosphates / Q000378:metabolism*; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009243:NAD / Q000378:metabolism; D051381:Rats; D013403:Sugar Phosphates / Q000378:metabolism
D005958:Glucosephosphates; D005994:Glycerophosphates; D007773:Lactates; D013403:Sugar Phosphates; D009243:NAD; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium