Enzymes glycogen

The next step involves a transfer of the glucose residue from UDP-glucose onto the glycogen primer through the aid of the enzyme glycogen synthetase ... 

A crucial kinase that functions as an intermediary in numerous intracellular signaling pathways is the enzyme glycogen synthase kinase-3 (GSK-3) 898... 

Figure 3.29 Control of an enzyme activity by multiple allosteric regulators. The enzyme glycogen phosphorylase b in muscle is regulated by changes in the concentrations of AMP and inosine monophosphate (IMP) (which are activators) and ATP and glucose 6-phosphate (G6P), which are inhibitors.

Since the enzyme glycogen synthase catalyses the rate-limiting step in glycogen synthesis, it is the activity of this enzyme that must be increased as the blood glucose concentration increases. This is achieved via an interconversion cycle (i.e. reversible phosphorylation). A protein kinase phosphorylates it, which inactivates the enzyme, whereas a protein phosphatase dephosphorylates it, which... 

Pyridoxine is present in food in the free form and as a glucoside, which may undergo partial hydrolysis in the gut lumen, or may be absorbed intact. Although pyridoxine is associated with the enzyme glycogen phosphorylase in muscles, it is not released in response to a dietary deficiency therefore it cannot be regarded as a storage form of the vitamin. 

The hormonal mechanisms of action to regulate glycogenesis and glycogenol-ysis involve reversible phosphorylation of the critical enzymes glycogen synthase and phosphorylase, respectively (Figure 6—6). 

In vivo linear a-l,4-glucans are synthesized from ADP-glucose by the enzyme glycogen synthase [94-97]. The enzyme, as well as the monomer, are quite sensitive and therefore most researchers (at least in the field of polymer science) prefer to use phosphorylase for the synthesis of amylose. 

Fmax of the enzyme glycogen phosphorylase from skeletal muscle is much greater than the I max of the same enzyme from liver tissue. 

Glycogen degradation requires two enzymes glycogen phosphorylase and glycogen-debranching enzyme. 

Fig. 6.8 Assuming a constant fluxJcNC from precursors to the pool of G6P, the hepatic glucose output HGO is more or less correlated to the changes in glycogen stores. The buildup of glycogen from G6P is controlled by the enzyme glycogen synthase, GgS, and the breakdown of glycogen is controlled by the enzyme glycogen phosphorylase, GgP.

Enzyme Activity and Physiological Function The Vmax of the enzyme glycogen phosphorylase... 

The modified glucose molecule is a substrate for the enzyme glycogen synthase ... 

Adrenaline exerts its effect by binding to a receptor site on the cell surfaces of liver and muscle cells, where it initiates a series of signals that ultimately causes an inactive form of the enzyme glycogen phosphorylase to become active. This enzyme is the first in a sequence that leads to the breakdown of glycogen to glucose and other products. 

In the liver and muscle cells, another enzyme, glycogen phosphorylase, breaks down glycogen into glucose molecules, which then enter glycolysis. 

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