Glucose-6-phosphatase formation

Golgi apparatus Glycosyl transferases, glucose-5-phosphatase, formation of plasma membrane and secretory vesicles... 

Both phosphorylase a and phosphorylase kinase a are dephosphorylated and inactivated by protein phos-phatase-1. Protein phosphatase-1 is inhibited by a protein, inhibitor-1, which is active only after it has been phosphorylated by cAMP-dependent protein kinase. Thus, cAMP controls both the activation and inactivation of phosphorylase (Figure 18-6). Insulin reinforces this effect by inhibiting the activation of phosphorylase b. It does this indirectly by increasing uptake of glucose, leading to increased formation of glucose 6-phosphate, which is an inhibitor of phosphorylase kinase. 

The reverse of this reaction does occur in some cells (e.g. hepatocytes), catalysed by the enzyme glucose-6-phosphatase, but the direction is always towards glucose formation, i.e. glucose 6-phosphate is never produced by this reaction in vivo. The question is, why not ... 

Flo. 6. Action of different concentrations of NaF on G-6-P (/imole) formation by human prostatic phosphatase in the presence of different amounts of phenyl phosphate and excess glucose. From Vescia and Chance Ul). 

The insulin-enhancing activity of vanadium compounds is likely to be related to their interactions with cellular redox chemistry and ROS formation, in addition to direct inhibition of PTP-1B and other protein phosphatases as a transition-state analogue [100], Differences in the effects of V (III, IV or V)-dipicolinic acid complexes on blood glucose and absorption of V into serum after chronic oral admin-... 

Glycolysis, the pentose phosphate pathway, the production of glycogen, and the formation of glucose (glucose-6-phosphatase). 

Figure 7.6. The metabolic reactions involved in the conversion of glycerol to glucose, the required precursor in the formation of sophorose. Note Reaction 1 catalyzed by triose phosphate isomerase. Reaction 2 catalyzed by aldolase. Reaction 3 catalyzed by fructose 1,6-bisphosphatase. Reaction 4 catalyzed by phosphoglucose isomerase., Reaction 6 catalyzed by glucose 6-phosphatase.

D-2) Glucftse 6-phosphatase deficiency Cl pe I GSD Von Gierke s Disease). There is a deficiency at this step in the formation of glucose by the liver. Glucose 6-phosphate instead forms other things and the flow of reactions shifts to ... 

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