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)

Hepatocytes were isolated from immature and adult rat liver by retrograde perfusion with calcium free buffer, followed by enzymic digestion, and separated into subpopulations by centrifugal elutriation. Several subpopulations with increasing cell diameters were distinguished. The smaller cells were attributed to the periportal area, the larger ones to the perivenous (centrilobular) region. Profiles of total cytochrome P-450 concentration, benzphetamine N-demethylation and ethoxyresorufin O-deethylation, NADPH-cytochrome c-reductase, glucose-6-phosphatase and glutamate-pyruvate-transaminase activities were determined in all subpopulations. With adult hepatocytes an increasing cytochrome P-450 concentration with increasing cell diameter (increasing from periportal to perivenous hepatocytes) could be observed, paralleled by increasing activities of benzphetamine N-demethylation and ethoxyresorufin O-deethylation activities. While NADPH-cytochrome c-reductase did not show a distinct zonation, glucose-6-phosphatase and glutamate-pyruvate-transaminase revealed increasing activities with increasing cell diameter. Immature hepatocytes (rats aged 11-15 days) were smaller, and more fragile. They could not be isolated with the same enzyme solution as adult hepatocytes and they did not show any zonation of cytochrome P-450 concentration, although the zonation of benzphetamine N-demethylation and ethoxyresorufin O-deethylation was almost fully developed. For NADPH-cytochrome c-reductase a zonation with higher activities in the perivenous cells could be demonstrated, in contrast to the lack of zonation in adult rats. Glucose-6-phosphatase activity showed a decline with increasing cell diameter in immature hepatocytes, whereas glutamate-pyruvate-transaminase activity did not show any zonation. In rats aged 20 days the zonation of these parameters in liver was in between that of younger and older animals. Zonation of the liver lobule develops postnatally with individual patterns for the different parameters.
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PMID:Separation and characterization of hepatocytes from immature and adult rats into distinct subpopulations by centrifugal elutriation. 322 57

Plasmodium yoelii nigeriensis infection in albino mice significantly altered the hepatic microsomal mixed function oxidase system. Cytochrome P-450 (the terminal monooxygenase) and other monooxygenases, viz. aniline hydroxylase, aminopyrine-N-demethylase and benzo(a)pyrene hydroxylase were significantly lowered while microsomal heme showed 4-fold increase at 80% parasitaemia. Noticeable impairment in the other components like NADH:cytochrome b5 reductase, NADPH:cytochrome c reductase, cytochrome b5 and glucose-6-phosphatase was also observed. Oral treatment of normal and P. y. nigeriensis infected mice with chloroquine (64 mg per kg body weight for 4 days) caused lowering of mixed function oxidase activities which however showed a recovering trend, a week after cessation of treatment.
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PMID:Effect of Plasmodium yoelii nigeriensis infection and chloroquine on the hepatic mixed function oxidase system of mice. 362 73

Hydroxylation of dimethylaniline in rabbit liver microsomes is accompanied by inactivation of cytochrome P-450 and the formation of products inhibiting the catalytic activity of non-inactivated cytochrome P-450. Other enzymes and electron carriers of microsomal membrane (cytochrome b5, NADH-ferricyanide reductase, NADPH-cytochrome c and NADPH-cytochrome P-450 reductases) as well as glucose-6-phosphatase were not inactivated in the course of the monooxygenase reactions. Phospholipids and microsomal membrane proteins were also unaffected thereby. Consequently, the changes in the microsomal membrane during cytochrome P-450 dependent monooxygenase system functioning are confined to the inactivation of cytochrome P-450.
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PMID:[Effect of monooxygenase reactions catalyzed by cytochrome P-450 on the microsomal membrane]. 366 48

Seminal plasma antioxidant inhibited ascorbate/iron-induced lipid peroxidation in spermatozoa, brain and liver mitochondria. The concentration required to produce inhibition in brain and liver mitochondria was high. Denaturation of spermatozoa resulted in complete loss of antioxidant action. Maintenance of native structure was essential for action of seminal plasma antioxidant in spermatozoal lipid peroxidation. The antioxidant inhibited NADPH, Fe3+-ADP induced lipid peroxidation in microsomes and consequences of lipid peroxidation such as glucose-6-phosphatase inactivation were prevented by presence of antioxidant. It did not inhibit microsomal lipid peroxidation induced by ascorbate and iron and xanthine-xanthine oxidase.
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PMID:Effect of seminal plasma antioxidant on lipid peroxidation in spermatozoa, mitochondria and microsomes. 406 52

The three Golgi fractions isolated from rat liver homogenates by the procedure given in the companion paper account for 6-7% of the protein of the total microsomal fraction used as starting preparation. The lightest, most homogeneous Golgi fraction (GF(1)) lacks typical "microsomal" activities, e.g., glucose-6-phosphatase, NADPH-cytochrome c-reductase, and cytochrome P-450. The heaviest, most heterogeneous fraction (GF(3)) is contaminated by endoplasmic reticulum membranes to the extent of approximately 15% of its protein. The three fractions taken together account for nearly all the UDP-galactose: N-acetyl-glucosamine galactosyltransferase of the parent microsomal fraction, and for approximately 70% of the activity of the original homogenate. Omission of the ethanol treatment of the animals reduces the recovery by half. The transferase activity is associated with the membranes of the Golgi elements, not with their content. Galactose is transferred not only to N-acetyl-glucosamine but also to an unidentified lipid-soluble component.
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PMID:Golgi fractions prepared from rat liver homogenates. II. Biochemical characterization. 435 72

The saturation of the fat contained in the diet has been observed to affect the acylcoenzyme A:cholesterol acyltransferase (ACAT) activity of rat liver microsomes. ACAT activity in microsomes (Mp) prepared from livers of rats fed a polyunsaturated fat-enriched diet containing 14% sunflower seed oil was 70-90% higher than in microsomes (Ms) prepared from livers of rats fed a saturated fat-enriched diet containing 14% coconut oil. This difference was observed within 20 days after the diets were begun, the earliest time tested, and persisted throughout the 70-day experimental period. The difference was noted at all [1-14C]palmitoyl CoA concentrations tested, 2.5-33 micronM, and at temperatures between 18 and 40 degrees C. Arrhenius plots revealed a single transition in enzyme activity, occurring at 29 degrees C in both microsomal preparations. Likewise, the activation energy above this transition was the same in Mp and Ms, 12.5 KCal/mol. Addition of albumin to the incubation medium increased the ACAT activity of both microsome preparations, but the difference between Mp and Ms persisted. Mp was enriched in polyenoic fatty acids, primarily 18:2 and 20:4, while Ms was enriched in monoenoic acids. Although the 20:4 increase in Mp occurred in all phosphoglycerides, it was especially pronounced in the serine and inositol phosphoglyceride fraction. There were no differences in the phospholipid or cholesterol content, phospholipid head group composition, or protein composition of the two microsomal preparations. The possibility is discussed that the changes in ACAT activity result from the differences in fatty acid composition of the microsomes. Other microsomal enzymes exhibited varying responses to these dietary fatty acid modifications. Palmitoyl CoA hydrolase and NADPH cytochrome c reductase activities were unchanged. UDP glucuronyl transferase activity was 50% higher in Mp, but glucose-6-phosphatase and NADH cytochrome b5 reductase activities were 25% higher in Ms. Therefore, dietary fat modifications do not produce a uniform effect on the activity of microsomal enzymes.
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PMID:Effect of dietary fat saturation on acylcoenzyme A:cholesterol acyltransferase activity of rat liver microsomes. 610 16

1. The NADPH-dependent lipid peroxidation process was studied with microsomes and also the effects of addition of superoxide dismutase, catalase and thiourea. Only catalase and thiourea were able to inhibit lipid peroxidation. It seems that the initiating radical is the OH. radical formed by the Fenton reaction. 2. During lipid peroxidation glucose-6-phosphatase is inactivated, whilst the microsomal enzyme palmitoyl-CoA hydrolase is practically not affected. Because glucose-6-phosphatase activity decreases during ageing and palmitoyl-CoA hydrolase does not, a possible relationship with the ageing process is thought to exist. 3. Chromolipids are formed by the NADPH-dependent lipid peroxidation. These chromolipids have the same excitation-emission spectra as described for lipofuscin. The formation of these chromolipids is blocked by the addition of catalase and thiourea. 4. High-molecular weight proteins are formed during the NADPH-dependent lipid peroxidation. This process can be associated with the inactivation of enzymes. Also polymerisation is prevented by catalase and thiourea.
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PMID:Lipid peroxidation of rat liver microsomes. 611 5

Metabolic alterations in ventromedial hypothalamus (VMH)-lesioned rats were investigated by examining daily changes of enzyme activities and urea concentrations three weeks after the operation. VMH-lesions in female adult rats caused a significant elevation in the activity of acetyl-CoA carboxylase in the liver and parametrial adipose tissue. These changes suggest an increased lipogenesis. VMH-lesions also elicited an increase in activities of glucokinase (GK), pyruvate kinase (PK) and fructose 1,6-bisphosphatase (FBPase), and a decrease in activities of phosphofructokinase (PFK), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) in the liver. The apparently inconsistent changes in activities of key glycolytic enzymes, GK, PK and PFK, and key gluconeogenic enzymes, G6Pase, PEPCK and FBPase in the liver may be explained by the fact that they were favorable for glucose oxidation through pentose phosphate cycle and provide NADPH for lipogenesis in the liver. Furthermore, VMH-lesions induced an increase in urea contents of the liver and serum, and elicited an increase in activity of liver tyrosine aminotransferase (TAT) and a decrease in activity of liver histidase. These changes suggest an accelerated amino acid and protein catabolism, and favor an increment in the supply of the substrate for lipogenesis. Daily rhythms of TAT, histidase activities and serum urea concentration observed in the control rats were abolished by VMH-lesions. These findings suggest that VMH-lesions elicit the loss of these daily rhythms, probably through the disturbance of the circadian rhythm of feeding behavior at this dynamic phase (three weeks after operation) of obesity.
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PMID:Shift of metabolism in rats with ventromedial hypothalamic lesions with respect to changes in daily rhythms of enzyme activity. 614 67

Crude microsomes from porcine endometrium and three subfractions obtained by a modification of Rothschild's technique were characterized by RNA/protein ratio, marker enzyme activities and morphological appearance. The microsomes were devoid of glucose-6-phosphatase activity. They contained approximately 10% of arylesterase-, approximately 30% of both NADPH-cytochrome reductase- and UDPgalactose-N-acetyl-glucosamine beta-D-galactosyltransferase- and approximately 60% of 5'-nucleotidase activities present in the homogenates. Subfraction I (smooth membranes) had twice the galactosyltransferase activity of Subfraction II (smooth and rough membranes + free ribosomes); both subfractions were rich in 5'-nucleotidase and cytochrome reductase activities. Subfraction III (rough membranes) had very low marker activities but exhibited the highest RNA/protein ratio, which was lowest in I.
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PMID:Characterization of microsomal subfractions from porcine endometrium cells. 619 68

The effects of medroxyprogesterone acetate (MPA) and phenobarbital (PB) on hepatic glucose and drug metabolism were investigated in male rats after liver injury, induced with dimethylnitrosamine (DMN). MPA normalized fasting blood glucose (BG) and serum immunoreactive insulin (IRI) levels and enhanced hepatic glucose-6-phosphatase (G6Pase) and NADPH cytochrome P450 reductase activities and glycogen and cytochrome P450 (cytP450) contents after liver injury. PB improved hepatic glycogen and cytP450 contents and NADPH cytP450 reductase activity in DMN pretreated rats. The increase in drug metabolism was more pronounced after PB than MPA therapy whereas MPA had more effect on glucose metabolism than had PB. This suggests that the inducing properties of these compounds diverge from each other.
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PMID:A comparison of the effects of phenobarbital and medroxyprogesterone acetate on drug and glucose metabolism in rats with chemical liver injury. 623 40


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