Sex-linked changes in immunoreactive glucose-6-phosphate dehydrogenase in rat liver

The level of hepatic immunoreactive glucose-6-phosphate dehydrogenase protein was found to correlate well with the enzyme activity in adult rats fed the stock laboratory diet in a variety of hormonal conditions. The amount of immunoreactive protein and enzyme activity was 2-fold greater in sexually mature female rats compared with aged matched male animals. However, this difference was absent in diabetic animals, and furthermore although triiodothyronine administration to the diabetic male rat could restore the level of enzyme activity to that of the normoglycaemic animal, it was much less effective in the female animal. In contrast, administration of insulin to the normoglycaemic animal increased the level of glucose-6-phosphate dehydrogenase in the female, but was without effect in the male. These results are discussed in relation to the possible role of thyroid status and steroid sex hormones in the regulation of hepatic glucose-6-phosphate dehydrogenase.     

Effectors of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of rat liver.

Summary The lower Vmax of 6PGDH with respect to G6PDH and its higher sensitivity to inhibition by NADPH, suggest the existence of an imbalance between the two dehydrogenases of the pentose phosphate pathway in rat liver. Possible modulators of these activities, particularly in relation with the inhibition by NADPH in physiological conditions, have been investigated. The results suggest that in both cases the inhibition by NADPH is strictly isosteric and that the relative affinities for the reduced and oxidized forms of the pyridine nucleotide are unaffected by glutathion, the intermediates of the pentose phosphate shunt or some divalent ions.Abbreviations G6PDH glucose-6-phosphate dehydrogenase (EC 1.1.1.49) - 6PGDH 6-phosphogluconate dehydrogenase (EC 1.1.1.44) On leave from the Instituto de Bioquímica, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.     

Preliminary crystallographic study of glucose-6-phosphate dehydrogenase from rat liver

Crystals of D-glucose-6-phosphate: NADP+ oxidoreductase were obtained with the hanging drop, vapor diffusion and batch methods from ammonium sulfate-containing solutions. X-ray diffraction photographs indicate that the crystals belong to the orthorhombic space groups I222 or I2(1)2(1)2(1) with unit cell dimensions of a = 66.0 A, b = 140.8 A and c = 177.8 A. These data, together with results from sodium dodecyl sulfate/polyacrylamide gel electrophoresis and crystal density experiments, indicate that there is one 116,000 Mr dimer per asymmetric unit. The crystals diffract to at least 2.2 A and are suitable for X-ray crystallographic structure determination.     

High activity of glucose-6-phosphate dehydrogenase in Kupffer cells isolated from rat liver

Summary Sinusoidal cells in the rat liver react intensively for G6DPH activity after appropriate incubation (Rieder et al. 1978). After isolation and purification of the sinusoidal Kupffer and endothelial cells, it was demonstrated that Kupffer cells exhibit a 5–8 times higher G6PDH activity on a per cell basis by comparison with endothelial cells, while the specific G6PDH activity was 3–4 times higher in Kupffer cells. The Kupffer cells can be divided into two groups which differ significantly in G6PDH activity calculated on a per cell basis. In histochemical studies, G6PDH can be used as a marker for Kupffer cell identification.     

Fructose-6-phosphate is not a substrate for glucose-6-phosphate dehydrogenase

D-Fructose-6-phosphate was shown not to be a substrate for glucose-6-phosphate dehydrogenases (EC. 1.1.1.49) from human erythrocytes, bovine adrenal, rat liver, three yeasts (brewer's yeast, baker's yeast, and Candida utilis), and Leuconostoc mesenteroides. These findings contrast with those of G.M. Kidder (J. Exp. Zool., 226:385-390, '83).