Adenosine triphosphate turnover

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

F. H. Westheimer (1987) has provided a detailed survey of the multifarious ways in which phosphorus derivatives function in living systems (Table 4.7). The particular importance of phosphorus becomes clear when we remember that the daily turnover of adenosine triphosphate (ATP) in the metabolic processes of each human being amounts to several kilograms Phosphate residues bond two nucleotides or deoxynucleotides in the form of a diester, thus making possible the formation of RNA and DNA the phosphate always contains an ionic moiety, the negative charge of which stabilizes the diester towards hydrolysis and prevents transfer of these molecules across the lipid membrane. 

FIGURE 14-6 Main signaling pathways for histamine receptors. Histamine can couple to a variety of G-protein-linked signal transduction pathways via its four different receptors. The Hj receptor activates the phosphatidylinositol turnover via Gq/11 proteins. The other receptors either positively (H2 receptor) or negatively (H3 and H4 receptor) regulate adenylyl cyclase activity via Gs and GUo protein activation respectively. Several additional signaling pathways have been described, which are not shown. Abbreviations PfP2, phosphatidylinositol 4,5-bisphosphate PIC, phospholipase C AC, adenylyl cyclase ATP, adenosine triphosphate cAMP, cyclic AMP PKC, protein kinase C PICA, protein kinase A. 

Adenosine deaminase (ADA) is a ubiquitous enzyme that is essential for the breakdown of the purine base adenosine, from both food intake and the turnover of nucleic acids. ADA hydrolyzes adenosine and deoxyadenosine into inosine and deoxyinosine, respectively, via the removal of an amino group. Deficiency of the ADA enzyme results in the build-up of deoxyadenosine and deoxyATP (adenosine triphosphate), both of which inhibit the normal maturation and survival of lymphocytes. Most importantly, these metabolites affect the ability of T-cells to differentiate into mature T-cells [656430], [666686]. ADA deficiency results in a form of severe combined immunodeficiency (SCID), known as ADA-SCID [467343]. 

Adenosine triphosphate (ATP) as a universal free energy transmitter undergoes the following turnover reaction ADP + Pi = ATP + H2O. This reaction represents a simplified synthesis of ATP and hydrolysis of ATP, which releases energy utilized in the transport processes. Enzyme-catalyzed reactions, including the electron transport chain and proton translocation, are composed of series of elementary reactions that proceed forward... 

The adenosine triphosphate (ATP) molecule is essential for life. It provides energy for muscle contraction, nerve conduction, many biochemical reactions, etc. At rest ATP turnover is 28 g (1 oz) of ATP per minute which is equivalent to 1.4kg (3 lb) per hour. During strenuous exercise, ATP turnover increases to a massive O.Skg/min Figure 10.1 shows that ATP consists of adenine, ribose and three phosphate groups that are identified as a-, P- and y-. Hydrolysis of the high energy phosphoanhydride bonds between the P- and y-phosphorus atoms, or alternatively, between the a- and P-phosphorus atoms releases energy for the biochemical reactions of life. 

Administration of glucose reduces the tucnover rate in postabsorptive state of phosphocreatine, adenosine triphosphate, and fructose-6-phosphate, but not that of glucose-6-phosphate. In fasting state, the administration of glucose does not affect the turnover rate of phosphocreatine and adenosine triphosphate. 

Manna s data (1991) of the efficacy of a nimodipine and lithium combination are of particular interest in reference to the above hypotheses related to combined effects on calcium-related mechanisms. Lithium obviously exerts complex effects on a variety of systems in brain, but its effects on phosphoinositide turnover and cyclic adenosine monophosphate and downstream effects on 1,4,5-inositol triphosphate (IP3) metabolism in calcium-related processes (as reviewed by Berridge 1989 H. L. Meltzer 1990 and... 

All cells require energy to live and reproduce. They get the energy they need from nutrients that they convert into a chemically useful form. The most important repository of chemical energy is adenosine 5 -triphosphate (ATP). The importance of ATP to biological reactions is reflected in its turnover rate in humans each day, a person uses an amount of ATP equivalent to his or her body weight. 

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