Glucose-6-phosphatase Activity

Cyprinus carpio 0.5 after 6 days, 300% increase in phosphorylase and 200% increase in glucose-6-phosphatase activities in liver increase in sugar level and serum lactic dehydrogenase activity 18... 

Di-tt-octylphthalate has been shown to be a mild liver toxin at high doses in acute- and intermediate-duration studies in rodents. While the mechanism of action for these hepatic effects is not known, di-w-octylphthalate does not appear to behave like other phthalate esters such as di(2-ethylhexyl)phthalate, which have been shown to be hypolipidemic peroxisome proliferators. Instead, the liver changes associated with exposure to di- -octylphthalate are characterized by marked centrilobular accumulation of fat and loss of glycogen, accompanied by reduced glucose-6-phosphatase activity and some centrilobular necrosis. 

Hepatio Renal Endoor 100 mg/kg/d 100 mg/kg/d 100 mg/kg/d (Increased Mg ATPase, acid phosphatase, and glucose-6-phosphatase activities) (Increased Mg ATPase activity) (Increased blood glucose) sulfate... 

No gross or microscopic lesions were observed in the kidneys of rats treated dermally with 100 mg nickel/kg/day as nickel sulfate for 15 or 30 days (Mathur et al. 1977). In this study, there was no indication that the rats were prevented from licking the nickel from the skin therefore, the animals could have been orally exposed. Increased Mg ATPase was observed in the kidneys of guinea pigs treated with 100 mg nickel/kg/day as nickel sulfate placed on skin of the back for 30 days (Mathur and Gupta 1994). No effect was noted at 15 days, and dermal nickel exposure had no effect on kidney acid phosphatase or glucose-6-phosphatase activities. 

Blank put together 50 pi sample (homogenate) and 5 pi sodium acetate buffer (total aliquot volume of 55 pi), incubate for 5 min at 37°C (glucose-6-phosphatase activity is destroyed while unspecific phosphatase activity is retained). 

In glycogenosis type lb (GSD I non-a ), glucose-6-phosphatase activity is normal or even elevated when measured in liver homogenates, but it is low when measured in a fraction of intact liver microsomes [10]. 

C. Glucose 6-phosphatase activity in RBCs removes the excess glucose 6-phosphate, thus resulting in cell damage. This does not happen in the hepato-cyte. 

The release of glucose from the glycogen stores in the liver is mediated by glucose 6-phosphatase, which is apparently embedded within the membranes of the endoplasmic reticulum. A labile enzyme, it consists of a 357-residue catalytic subrmit,251/252 which may be associated with other subunits that participate in transport.252 253 A deficiency of this enzyme causes the very severe type la glycogen storage disease (see Box 20-D).251 253 Only hepatocytes have significant glucose 6-phosphatase activity. 

Although glucose-6-phosphatase activity in the nuclear fraction which has generally been observed may in part result from contamination of nuclear preparations with unruptured cells and debris, activity has also been observed with purified nuclei (62). Further, Kashnig and Kasper (63) have recently identified glucose-6-phosphatase as a component of rat liver nuclear membrane. 

Ogorodnikova, L.G. and Lebedinskaya, I.N. (1984). Glycogen content, phosphorylase and glucose-6-phosphatase activity in fast and slow muscles of carp (hi Russian). Zhumal Evolutsionnoy Biokhimii i Physiologii 20,12-15. 

QUESTION 8.6 Patients with Von Gierke s disease (a glycogen storage disease) lack glucose-6-phosphatase activity. Two prominent symptoms of this disorder are fasting hypoglycemia and lactic acidosis. Can you explain why these symptoms occur ... 

Without glucose-6-phosphatase activity, the individual cannot release glucose into the blood. Blood glucose levels must be maintained by frequent consumption of carbohydrate. Excess glucose-6-phosphate is converted to pyruvate, which is then reduced by NADH to form lactate. 

It enables the hexose moiety from phosphorylated glucose to be released into the bloodstream. It is present in the endoplasmic reticulum of liver and kidney, but activity in brain and skeletal musde is generally low. Glucosyl units, after their removal from liver glycogen by phosphorylase, can ako be released into the bloodstream. Glycogen, present in skeletal muscle, is used almost exclusively within muscle itself. Low glucose 6-phosphatase activities have been detected in the pectoral muscles of domestic fowl pigeon and house sparrow (Lackner et al, 1984). This may be an indication that small... 

Asotra, K. (1986). Glucose-6-phosphatase activity in rtormal and denervated developing chick gastrocnemii reappraisal of glycogenolytic and glycolytic metabolism in skeletal muscle. Exp. Path., 29, 103-12. 

In mice orally administered 500 mg/kg of a holy basil aqueous extract daily for 15 days, a reduction in serum thyroxine (T4) concentrations and glucose-6-phosphatase activity was observed. Serum levels of triiodothyronine (T3) and the T3/T4 ratio were unaffected (Panda and Kar... 

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