Glycogen metabolism termination

Pyridoxal phosphate is a coenzyme for many enzymes involved in amino acid metabolism, especially in transamination and decarboxylation. It is also the cofactor of glycogen phosphorylase, where the phosphate group is catalytically important. In addition, vitamin Bg is important in steroid hormone action where it removes the hormone-receptor complex from DNA binding, terminating the action of the hormones. In vitamin Bg deficiency, this results in increased sensitivity to the actions of low concentrations of estrogens, androgens, cortisol, and vitamin D. 

In animal fermentations, an organic molecule (e.g., pyruvate) serves as a terminal proton and electron acceptor, forming an organic end product (e.g., lactate). In contrast, 02 is required as a terminal acceptor for the complete oxidation of substrates such as glucose, glycogen, fatty acids, or amino acids. As discussed in chapter 3, 02 was not always available as one of the substrates for oxidative metabolism and organisms in primordial times had to rely on anaerobic metabolic processes. 

At the end of the experiment, the rats are terminally anesthetized, the abdomen is opened, and terminal blood collection is performed from the vena cava caud. or the aorta abdominalis for determination of metabolic blood parameters and insulin. A part of the liver is freeze clamped immediately as well as a part (about 1 gr) of skeletal muscle (e.g. M. gastrocne-micus). The frozen tissue is stored in liquid nitrogen for subsequent determinations of intrahepatic and intramuscular concentrations of glycogen, glucose-6-phosphate (G6P) and ATR In liver samples hepatic... 

FFA, free fatty acid GH, growth hormone GLP-1, glucagon-like protein 1 GS, glycogen synthase GSK3, glycogen synthase kinase 3 HDL, high density lipoprotein HF, heart failure IKK, inhibitor of kappa B kinase INK, c-jun N-terminal kinase EDL, low density lipoprotein Ep(a), lipoprotein little a EV, left ventricular MetS, metabolic syndrome MI, myocardial infarction... 

Apart from fhree PKA phosphorylation sites described above, HSL is phosphorylated in vivo in hormonally quiescent cells at a site named the basal site [235], corresponding to Ser-565 in rat HSL [232, 234], i.e. two residues carboxy-terminal to Ser-563. Glycogen synfhase kinase-4 [237], Ga /calrrioduliri-dcpendent kinase II, and AMP-activated protein kinase (AMPK) [238] phosphorylate Ser-565 in vitro without any direct effect on enzyme activity (Fig. 11.5). AMPK has been proposed to be the physiologically relevant kinase [238], based on its involvement in ofher aspects of lipid metabolism and on its proposed role as fuel gauge [239]. Furthermore, because phosphorylation by AMPK prevented subsequent phosphorylation of Ser-563, and vice versa, it was proposed fhat phosphorylation of Ser-565 exerts an antilipolytic role [238]. This proposal is supported by experiments showing that preincu-... 

The intermediary metabolism of carbohydrate is discussed in Chapter 4, to which the reader is referred for details of the enzymatic conversion of hexoses, the formation of glycogen, and the Embden-Meyerhof scheme of glycolysis. Terminal oxidation of carbohydrate is also discussed the oxidation and reactions of pyruvic acid, the monophosphate shunt, and the tricarboxylic acid cycle are illustrated diagrammatically. 

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