Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycogen content and six major enzymatic activities involved in glycogen metabolism were analysed in chorionic villi (CV). Glycogen levels were found to be lower than those known to exist in liver and muscle. Activities of alpha-glucosidase, amylo-1,6-glucosidase, phosphorylase b and phosphorylase kinase were detectable by standard methods. The enzymatic activities of glucose-6-phosphatase and phosphorylase a were undetectable. These findings suggest that CV biopsies can be useful for first-trimester diagnosis of glycogen storage disease types II, III and VI, but not for type I (glucose-6-phosphatase deficiency).
Placenta
PMID:Enzymatic activity of glycogen metabolism in chorionic villi. 302 29

In an attempt to explain the previous observation of the rise and subsequent fall in glycogen content of the rat visceral yolk sac during the latter half of gestation, the activities of glycogen phosphorylase, glucose-6-phosphatase and lysosomal alpha-glucosidase were measured. Glycogen phosphorylase was found to be present in the yolk sac and, as in adult rat liver, was predominantly in the 'a' (active) form. The specific activity of the enzyme was lower than in adult rat liver, when expressed per mg tissue protein or per mg tissue wet weight, but similar when expressed per mg tissue glycogen. Phosphorylase activity in yolk sac was similar at 16.5 and 18.5 days of gestation. Glucose-6-phosphatase activity was not detectable in the yolk sac at either 15.5 or 18.5 days of gestation. Two lysosomal enzymes, acid alpha-glucosidase and N-acetyl-beta-hexosaminidase, were shown to be present in the yolk sac at higher specific activity than in adult liver. Alpha-Glucosidase activity in yolk sac was similar at 15.5 and 18.5 days of gestation. It is concluded that the net degradation of yolk sac glycogen initiated around 18.5 days of gestation does not serve to provide glucose for the fetus, and may indicate an increased demand for metabolic energy within the yolk sac itself.
Placenta 1995 Dec
PMID:Glycogen metabolism in the rat visceral yolk sac. 2. Activity of glycogen-degrading enzymes. 871 Aug 2

The purpose of the present study was to localize glucose-6-phosphatase (G6Pase) activity in the human placenta at various gestational stages and to compare them to pre-eclamptic placenta activity. Ultrastructural enzyme-histochemical analysis of G6Pase was performed using cerium and lead as capturing agents. Precipitates indicative of G6Pase activity were observed in the endoplasmic reticulum and the nuclear envelope of the syncytiotrophoblasts in near-term placenta obtained from women with normal pregnancies. In placenta taken from women with severe pre-eclampsia, the localization pattern, enzyme activity intensity, and morphology of the endoplasmic reticulum did not differ from normal pregnancies. Stringent control experiments were performed also to ensure specific detection of G6Pase activity. The results indicate that cytochemically detectable G6Pase is present in the human placenta. This enzyme may play significant roles in carbohydrate metabolism in the human placenta.
Placenta 1999 Jan
PMID:Glucose-6-phosphatase is present in normal and pre-eclamptic placental trophoblasts: ultrastructural enzyme-histochemical evidence. 995 Jan 48

The human placenta transports glucose by facilitated diffusion down a concentration gradient from mother to fetus. It has previously been considered incapable of glucose synthesis. However, recent work has demonstrated the presence in placental tissue of glucose-6-phosphatase, which is required for the final step in the synthesis of glucose. Following continuous intravenous infusion into the maternal circulation of the stable isotope, 6,6-(2)H(2)glucose, during elective caesarean section, we have observed isotope dilution in the umbilical vein, without further dilution in the umbilical artery. Using a mathematical model containing maternal, placental and fetal compartments, the data were compatible with the release of glucose by the placenta. We conclude that the human placenta at term can produce glucose.
Placenta 1999 Sep
PMID:Glucose production by the human placenta in vivo. 1094 Feb 12

The present study was designed to localize some important enzymes, such as adenosine diphospate-degrading enzyme (ADP-degrading enzyme) (plasma membrane enzyme), cytochrome c oxidase (mitochondrial enzyme) and glucose-6-phosphatase (endoplasmic reticulum enzyme), in placentae from patients with idiopathic fetal growth restriction (FGR) associated with absent end-diastolic flow velocity in the fetal umbilical artery. We compared these enzyme activities and their localization patterns to those in placentae both from pre-eclampsia with FGR and normal pregnancy with appropriate for their gestational age infants. In idiopathic FGR placentae, the intensity and localization patterns of these three enzymes did not differ from those seen in the placentae from normal pregnancy. Decreased ADP-degrading enzyme activity and cytochrome c oxidase negative mitochondria, which were characteristic features of pre-eclamptic trophoblasts, were absent from trophoblasts of the idiopathic FGR placentae. These observations indicated that enzyme-cytochemically detectable trophoblastic cell dysfunction may be absent in idiopathic FGR, or if present, there is less functional impairment of each trophoblast in this disease than in pre-eclampsia. Though both idiopathic FGR and pre-eclampsia lead to placental insufficiency, and finally to restricted fetal growth, a different mechanism and pathophysiology may work at the cellular and subcellular levels in these two diseases.
Placenta
PMID:Placenta of idiopathic fetal growth restriction: cytochemically detectable enzyme activities do not change at a subcellular level. 1073 50

Glucose transfer from mother to fetus by placental facilitated diffusion is the dominant mechanism by which the fetus acquires glucose. In small for gestational age pregnancies, fetal glucose concentrations tend to be lower than normal and this persists following delivery. GLUT1 is the major glucose transporter in human placenta but there is no evidence of GLUT1 deficiency as a cause of the lower fetal glucose concentration in small for gestational age pregnancy. The physiological and pathological roles of the other glucose transporters (and there are 14 currently described) are unknown. In recent years, the possibility has been raised that the placenta is itself capable of supplying glucose for fetal needs. This hypothesis derived from glucose isotope studies in normal pregnancy, where dilution of glucose isotope was demonstrated in blood samples taken from the fetal circulation during intravenous infusion of glucose isotope in the mother. Although other gluconeogenic enzymes were known to be present, the placenta was previously considered incapable of glucose secretion because it lacked functional glucose-6-phosphatase. Recent studies, however, have suggested that specific glucose-6-phosphatase may be present in placenta but it may be the product of a different gene from conventional hepatic glucose-6-phosphatase. The presence of the specific transporters necessary for glucose-6-phosphatase activity is currently being investigated. The role of placental glucose secretion in normal and growth-restricted pregnancies is an area of current study.
Placenta 2006 Apr
PMID:Glucose production in the human placenta. 1661 44