Cellular phosphate metabolism

Menadione (vitamin K3),phylloquinone (vitamin Kj), and ascorbate (vitamin C) have been used to donate electrons to cytochrome c. For example, ascorbate is oxidized to dehydroascorbate as it uses its electrons to reduce cytochrome c directly. The dehydroascorbate is quickly reduced to ascorbate in the mitochondrion by NADH or FADH2. Menadione appears to improve cellular phosphate metabolism and to enhance electron transfer after a respiratory Complex I block. 

P. K. Holahan, S. A. Knizner, C. M. Gabriel and C. E. Swenberg (1988). Alterations in phosphate metabolism during cellular recovery of radiation damage in yeast. Int. J. Radiat., 54, 545-562. 

K. Yoshida, Z. Kuromitsu, N. Ogawa, K. Ogawa and Y. Oshima (1987). Regulatory circuit for phosphatase synthersis in Saccharomyces cerevisiae. In Phosphate metabolism and cellular regulation in microorganisms. Washington, Amer. Soc. Microbiol., pp. 49-55. 

In Phosphate Metabolism and Cellular Regulation in Microorganisms (A. Torriani-Gorini, F.G. Rothmann, S. Silver, A. Wright, E. Yagil, eds), pp. 156-8. American Society for Microbiology, Washington, DC. 

Glutathione peroxidase utilizes GSH to reduce the peroxides generated by cellular aerobic metabolism. GSH is regenerated from its oxidized form, GSSG, by glutathione reductase. NADPH, the reducing agent in this reaction, is supplied by the pentose phosphate pathway and several other reactions. 

Raisz LG (1990) The role of prosta andins in the local regulation of bone metabolism. In Bronner F, Peterlik M, eds. Molecular and Cellular Regulation of Calcium and Phosphate Metabolism, pp. 195-203. Alan Liss Inc. New York. 

The phosphates of the four ribonucleosides represented in RNA are found in virtually all cells, with erythrocytes being exceptional in that not all four ribonucleosides are represented in some nonnucleated cells. Nucleotide coenzymes and conjugated nucleotides are present in patterns which are characteristic of the tissue sample. These compounds are all nucleoside 5 -phosphate esters and the triphosphates are the most abundant species under conditions adequate for the mainteiiance of cellular energy metabolism. The nucleotide composition of a variety of animal tissues is discussed by Mandel (22) we will consider only several. 

To this point, the pathway has generated a pool of pentose phosphates. The AG° for each of the last two reactions is small, and the three pentose-5-phosphates coexist at equilibrium. The pathway has also produced two molecules of N/ DPH for each glucose-6-P converted to pentose-5-phosphate. The next three steps rearrange the five-carbon skeletons of the pentoses to produce three-, four-, six-, and seven-carbon units, which can be used for various metabolic purposes. Why should the cell do this Very often, the cellular need for... 

Phosphorylation is the reversible process of introducing a phosphate group onto a protein. Phosphorylation occurs on the hydroxyamino acids serine and threonine or on tyrosine residues targeted by Ser/Thr kinases and tyrosine kinases respectively. Dephosphorylation is catalyzed by phosphatases. Phosphorylation is a key mechanism for rapid posttranslational modulation of protein function. It is widely exploited in cellular processes to control various aspects of cell signaling, cell proliferation, cell differentiation, cell survival, cell metabolism, cell motility, and gene transcription. 

W. C. Plaxton, Metabolic aspects of phosphate starvation in plants. Phosphorus in Plant Biology Regulatory Roles in Molecular, Cellular, Organi.smic, and Eco.sy.s-lein Proces.ses (J. P. Lynch and J. Deikman eds.), American Society of Plant Physiologists, 1998, p. 229. 

Potassium is the second most abundant cation in the body and is found primarily in the intracellular fluid. Potassium has many important physiologic functions, including regulation of cell membrane electrical action potential (especially in the myocardium), muscular function, cellular metabolism, and glycogen and protein synthesis. Potassium in PN can be provided as chloride, acetate, and phosphate salts. One millimole of potassium phosphate provides 1.47 mEq of elemental potassium. Generally, the concentration of potassium in peripheral PN (PPN) admixtures should not exceed 80 mEq/L (80 mmol/L). While it is safer to also stick to the 80 mEq/L (80 mmol/L) limit for administration through a central vein, the maximum recommended potassium concentration for infusion via a central vein is 150 mEq/L (150 mmol/L).14 Patients with abnormal potassium losses (e.g., loop or thiazide diuretic therapy) may have higher requirements, and patients with renal failure may require potassium restriction. 

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