Erythrocyte glucose-6-phosphate dehydrogenase from Brazilian opossum Didelphis marsupialis.

In a comparative study of erythrocyte metabolism of vertebrates, the specific activity of glucose-6-phosphate dehydrogenase (G6PD) of the Brazilian opossum Didelphis marsupialis in a hemolysate was shown to be high, 207 +/- 38 IU g-1 Hb-1 min-1 at 37 degrees C, compared to the human erythrocyte activity of 12 +/- 2 IU g-1 Hb-1 min-1 at 37 degrees C. The apparent high specific activity of the mixture led us to investigate the physicochemical properties of the opossum enzyme. We report that reduced glutathione (GSH) in the erythrocytes was only 50% higher than in human erythrocytes, a value lower than expected from the high G6PD activity since GSH is maintained in a reduced state by G6PD activity. The molecular mass, determined by G-200 Sephadex column chromatography at pH 8.0, was 265 kDa, which is essentially the same as that of human G6PD (260 kDa). The Michaelis-Menten constants (Km: 55 microM) for glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (Km: 3.3 microM) were similar to those of the human enzyme (Km: 50-70 and Km: 2.9-4.4, respectively). A 450-fold purification of the opossum enzyme was achieved and the specific activity of the purified enzyme, 90 IU/mg protein, was actually lower than the 150 IU/mg protein observed for human G6PD. We conclude that G6PD after purification from the hemolysate of D. marsupialis does not have a high specific activity. Thus, it is quite probable that the red cell hyperactivity reported may be explained by increased synthesis of G6PD molecules per unit of hemoglobin or to reduced inactivation in the RBC hemolysate.

Erythrocyte glucose-6-phosphate dehydrogenase from Brazilian opossum Didelphis marsupialis

In a comparative study of erythrocyte metabolism of vertebrates, the specific activity of glucose-6-phosphate dehydrogenase (G6PD) of the Brazilian opossum Didelphis marsupialis in a hemolysate was shown to be high, 207 ± 38 IU g-1 Hb-1 min-1 at 37°C, compared to the human erythrocyte activity of 12 ± 2 IU g-1 Hb-1 min-1 at 37°C. The apparent high specific activity of the mixture led us to investigate the physicochemical properties of the opossum enzyme. We report that reduced glutathione (GSH) in the erythrocytes was only 50 percent higher than in human erythrocytes, a value lower than expected from the high G6PD activity since GSH is maintained in a reduced state by G6PD activity. The molecular mass, determined by G-200 Sephadex column chromatography at pH 8.0, was 265 kDa, which is essentially the same as that of human G6PD (260 kDa). The Michaelis-Menten constants (Km: 55 æM) for glucose-6-phosphate and nicotinamide adenine dinucleotide phosphate (Km: 3.3 æM) were similar to those of the human enzyme (Km: 50-70 and Km: 2.9-4.4, respectively). A 450-fold purification of the opossum enzyme was achieved and the specific activity of the purified enzyme, 90 IU/mg protein, was actually lower than the 150 IU/mg protein observed for human G6PD. We conclude that G6PD after purification from the hemolysate of D. marsupialis does not have a high specific activity. Thus, it is quite probable that the red cell hyperactivity reported may be explained by increased synthesis of G6PD molecules per unit of hemoglobin or to reduced inactivation in the RBC hemolysate.

Valores de referência de fibrinogênio plasmático em macaco prego (Cebus apella), anestesiado com Quetamina / Normal values of plasma fibrinogen in Cebus apella monkeys iunder ketamine anesthesia

Determinaram-se os valores de referência de fibrinogênio plasmático em macaco prego (Cebus apella). Para tanto, utilizaram-se 108 animais sadios, dos quais 53 machos (12 jovens e 41 adultos) e 55 fêmeas (20 jovens e 35 adultas), submetidos, previamente, a exame clínico. A coleta do material (sangue) foi realizada por punçäo da veia femoral direita e/ou esquerda com os animais anestesiados com quetamina, por via intramuscular, na dose de 10 mg/kg. A determinaçäo da fibrinogenemia foi realizada no soro, obtido após centrifugaçäo do sangue, segundo técnica descrita por Schalm et al.15 (1975)