Glucagon activity

Pyruvate kinase possesses allosteric sites for numerous effectors. It is activated by AMP and fructose-1,6-bisphosphate and inhibited by ATP, acetyl-CoA, and alanine. (Note that alanine is the a-amino acid counterpart of the a-keto acid, pyruvate.) Furthermore, liver pyruvate kinase is regulated by covalent modification. Flormones such as glucagon activate a cAMP-dependent protein kinase, which transfers a phosphoryl group from ATP to the enzyme. The phos-phorylated form of pyruvate kinase is more strongly inhibited by ATP and alanine and has a higher for PEP, so that, in the presence of physiological levels of PEP, the enzyme is inactive. Then PEP is used as a substrate for glucose synthesis in the pathway (to be described in Chapter 23), instead... 

Sapse, A.-M., M. Mezei, D. C. Jain, and C. Unson. 1994. Ab Initio Study of Aspartic and Glutamic Acid Supplementary Evidence for Structural Requirements at Postition 9 for Glucagon Activity. J. Mol. Struct. (Theochem) 306, 225-233. 

Insulin (inhibits) glucagon (activates) by their control of PFK-2 (produces fructose 2,6-bisP)... 

On the other hand, glucagon actively promotes gluconeogenesis by stimulating PEP car-boxykinase, and also promotes glycogenolysis and hpolysis. 

Liver glycogen phosphorylase exists in an inactive, de-phosphorylated form and in at least one active, phospho-rylated form. Conversion of phosphorylase b to phosphorylase a is catalyzed by phosphorylase kinase, which is activated by vasopressin, angiotensin II, and a-adrenergic agonists (mediated by Ca +) and by glucagon (which elevates cAMP). Glucagon activation of phosphorylase is in some way antagonized by insulin. 

Titled Vegen Proteins May Reduce the Risk of Cancer, Obesity, and Cardiovascular Disease by Promoting Increased Glucagon Activity, the indicators are that veggie proteins are high in the nonessential amino acids and low in the essential amino acids. (The inverse occurs in animal proteins.) The result is the increased production of glucagon, which has anticancer activity. 

Thus, the effect of enhanced glucagon activity can therefore be viewed as an anticancer condition, and is signaled by a person (usually) having hypoglycemia, or low blood sugar. 

On the other hand, glycolysis is favored by reduced glucagon activity and increased insulin activity, resulting in the inverse diabetic condition of hypoglycemia, or low blood sugar. That is, the sugar in the blood is more readily converted to its end products. 

Phosphoenolpyruvate carboxykinase (PEPCK) - This enzyme has no known allosteric regulators. The enzyme is controlled by hormonal regulation of its synthesis. The hormone, glucagon, activates transcription of the structural gene for the enzyme. Insulin, on the other hand, inhibits transcription of the gene. 

Glucagon activates transcription of phosphoenolpymvate carboxykinase Insulin represses transcription of phosphoenolpyruvate carboxykinase.. 

Between meals, a decreased insulin level and increased levels of insulin counter-regulatory hormones (e.g., glucagon) activate hpolysis, and free fatty acids are transported to tissues bound to serum albumin. Within tissnes, energy is derived from oxidation of fatty acids to acetyl CoA in the pathway of -oxidation. Most of the enzymes involved in fatty acid oxidation are present as 2-3 isoenzymes, which have different but overlapping specificities for the chain length of the fatty acid. Metabolism of unsaturated fatty acids, odd-chain-length fatty acids, and medium-chain-length fatty acids requires variations of this basic pattern. The acetyl CoA produced from fatty acid oxidation is principally oxidized in the TCA cycle or converted to ketone bodies in the liver. 

GLUCAGON ACTIVATES A PHOSPHORYLATION CASCADE THAT CONVERTS GLYCOGEN PHOSPHORYLASE b TO GLYCOGEN PHOSPHORYLASE a... 

Quant, PA., Tubbs, P.K. Brand, M.D. (1990)i ur. J. Biochem. 187, 169-174. Glucagon activates mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase in vivo by decreasing the extent of succinylation of the enzyme. 

Since glucagon activates adenyl-cyclase, which converts ATP to cyclic-AMP it is possible to speculate that the inhibitory effect of glucagon on the A6 desaturase is produced through a rise of the intracellular level of cyclic-AMP. The data of Table 3 confirm that dibutyryl c AMP administration to refeeding rats evokes the same effect as glucagon. 

Cell volume decrease occurs after exercise and other stresses, including normal life functions. During cell shrinkage — caused by oxidative and exercise stress, " glucagon activation,and high urea concentration — the following events take place ... 

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