Glucose-6-phosphatase intracellular

Fig. 3. Proposed mechanism involving hydrolytic and synthetic activities of glucose-6-phosphatase in the transport of glucose between intracellular and extracellular compartments. The shaded area represents the cross-sectional view of endoplasmic reticulum. E and E" are modified forms of glucose-6-phosphatase displaying principally phosphohydrolase and principally phosphotransferase activities, respectively. Differential influences of the intra- and extracellular milieu are postulated to maintain molecules of the enzyme selectively as E or E". Additional details are given in Section II,D.

In LLC-PKj cells gentamicin induces membrane damage as shown by the loss of specific membrane enzymes (y-glutamyl transpeptidase, alkaline phosphatase and aminopeptidase), a decrease of the lysosomal enzyme N-acetyl-P-D-glucosaminidase, an inhibition of apical Na -dependent glucose transporter and the basolateral Na-K-ATPase pump as well as a decrease in dome formation [141, 142]. Furthermore gentamicin results in a dose dependent decrease in intracellular ATP and cAMP [142]. 

The liver is also affected by epinephrine in this case, the a-1 receptors are activated by epinephrine. This will cause an increase in intracellular liver Ca2+, via IP3, an allosteric activator of phosphorylase kinase which will catalyze the phosphorylation of phosphorylase and thereby activation. This increase in active phosphorylase will rapidly increase glycogenolysis and provide hexosphosphates, which in the case of liver are not used primarily for glycolysis but, via the action of glucose-6-phosphatase, augment the blood glucose levels (Fig. 16.10). 

Glucose-6-phosphatase - This enzyme is not known to be allosterically controlled. Its Km for G6P is far higher than intracellular concentrations of the metabolite. Intracellular activity is controlled in first-order fashion by the concentration of G6P. 

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