Adenosine 5 -triphosphate metal complexes

Adenosine-5 -monophosphate lanthanide complexes NMR, 3,1104 Adenosine phosphates metal complexes, 2, 977 6, 445 Adenosine 5 -triphosphate... 

An important tetradentate ligand is adenosine triphosphate (ATP), which binds to divalent metal ions (such as Mg2+, Mn2+, Co24, and Ni2+) through four of their six coordination positions (Figure 12-2). The fifth and sixth positions are occupied by water molecules. The biologically active form of ATP is generally the Mg2+ complex. 

The simplest use of manganese is as part of a metal cofactor such as manganese(II) adenosine triphosphate, [Mn(II)ATP2-]. The metal complex is usually found as the bidentate [Mn(II)0,7-ATP2 ] (3, 4) as illustrated in Figure 1. Enzyme specificity for Mg(II), Mn(II), or Ca(II) ATP complexes is dependent on a variety of factors however, once selected, each metal apparently functions in an analogous manner. The metal ion serves two main purposes. First, based on the coordination geometry... 

Chapters 3-5 have described the calculation of various transformed thermodynamic properties of biochemical reactants and reactions from standard thermodynamic properties of species, but they have not discussed how these species properties were determined. Of course, some species properties came directly out of the National Bureau of Standard Tables (1) and CODATA Tables (2). One way to calculate standard thermodynamic properties of species not in the tables of chemical thermodynamic properties is to express the apparent equilibrium constant K in terms of the equilibrium constant K of a reference chemical reaction, that is a reference reaction written in terms of species, and binding polynomials of reactants, as described in Chapter 2. In order to do this the piiTs of the reactants in the pH range of interest must be known, and if metal ions are bound, the dissociation constants of the metal ion complexes must also be known. For the hydrolysis of adenosine triphosphate to adenosine diphosphate, the apparent equilibrium constant is given by... 

The conformations of nucleotides have been probed by lanthanides [73]. Furthermore, adenosine triphosphate (ATP)-lanthanide complexes are strong enough to carry the metal on to enzymes. Thus, Gd " competitively inhibits Mg -(yeast)-phosphoglycerate kinase (mol. wt. 47000) and selectively broadens histidine H resonances [74]. 

Cayley and Hague [70a] have employed the temperature-jump relaxation method to measure the rate of formation and dissociation of the 1 1 complex of magnesium(II) and 5-nitrosalicyclic acid (NSA) and also of the ternary complexes formed between this ligand and Mg(II) nitrilotriacetate (NTA), adenosine triphosphate (ATP) and polytriphosphate (TP) complexes, the last in an effort to gather information about the effect of bound ligands on the rate of substitution of a metal ion by a second type of group. It is expected that the presence of a bound ligand should... 

Adenosine triphosphate alkali metal complexes, 34 vanadyl complexes, 568 Alane, 123 amine adducts, 107 phosphine adducts, 111 Alane, alkoxy-, 124 Alane, amino-, 109 Alane, imino-, 109 Alkali metal complexes, 1-70 acid anions, 30 acid salts, 30 bipyridyl, 13 crown ethers cavity size, 38 cryptates... 

Ion-binding studies with biological molecules can be important in elucidating fundamental biochemical reaction systems in relation to bioenergetics, enzyme activation and membrane transport [182]. For example, the adenosine triphosphate (ATP)—adenosine diphosphate (ADP) cycle is one of the processes of primary importance to cellular energy systems and association constants determined [427—430] for metal—ATP and metal—ADP complexes are therefore of considerable interest Table 2.5). The constants may be obtained from measure-... 

Figure 13-2 (a) Structure of adenosine triphosphate (ATP), with ligand atoms shown in color. ib) Possible structure of a metal-ATP complex, with four bonds to ATP and two bonds to H2O ligands. 

Phytic acid and camosine (histidine-containing dipeptide), obtained from cereal and meat by-products, are effective inhibitors of hpid oxidation by several mechanisms, including metal inactivation and free radical quenching. Uric acid obtained from the decomposition of adenosine triphosphate in muscle also inhibits lipid oxidation by the same mechanisms. However, the importance of uric acid as an endogenous antioxidant in muscle foods is not clear. Various protein concentrates from soybeans, cottonseed and peanuts inhibit hpid oxidation in muscle foods. In addition to their iron binding activity, these crade extracts contain complex polyphenolic flavonoids that have potent antioxidant activity. 

The 3, 5 -cyclic monophosphate of adenosine (cAMP) (2.148) is an important secondary messenger for intercellular communication in biochemistry. When the cell is stimulated by the first messenger, compound 2.148 is formed from adenosine triphosphate (ATP) (Scheme 2.25). This reaction is catalysed by an adenosine cyclase enzyme. The cAMP then goes on to activate other intracellular enzymes, so producing a cell response. The response is terminated by the hydrolysis of cAMP by phosphodiesterase (a phosphate-ester-hydrolysis enzyme). The action of adenylate cyclase has been mimicked successfully with a p-cyclodextrin complex of Pr(iii) and other lanthanide(iii) metals, under physiological conditions. The... 

Metal cofactors do not always bind to the enzyme but rather bind to the primary substrate. The resulting substrate-metal complex binds to the enzyme and facilitates its activity. Creatine kinase catalyses the transfer of phosphoryl groups from adenosine triphosphate (ATP), which is broken down to adenosine diphosphate (ADP). The reaction requires the presence of magnesium ions. These, however, do not bind to the enzyme but bind to ATP, forming an ATP Mg complex. It is this complex that binds to the enzyme and allows transfer of the phosphoryl group ... 

Chemical reactions between biochemical compounds are enhanced by biological catalysts called enzymes, which consist mostly or entirely of globular proteins. In many cases a cofactor is needed to combine with an otherwise inactive protein to produce the catalytically active enzyme complex. The two distinct varieties of cofactors are coenzymes, which are complex organic molecules, and metal ions. Enzymes catalyze six major classes of reactions 1) Oxidoreductases (oxidation-reduction reactions), 2) Transferases (transfer of functional groups), 3) Hydrolases (hydrolysis reactions), 4) Lyases (addition to double bonds, 5) Isomerases (isomerization reactions) and 6) Ligases (formation of bonds with ATP (adenosine triphosphate) cleavage) [1]. 

Association of the hydrophobic tails of membrane lipids leads, as depicted in Fig. 4.47a, to what Watkins [341] has described as polar discontinuities. Transition to the micellar state is considered to be essential to allow cell fusion to occur as the biomolecular leaflet is thermodynamically a stable system which would resist coalescence with similar structures. External influences can, however, induce phospholipid aggregation and can thus alter the permeability of cell membranes to water-soluble and oil-soluble species. Calcium ions, for example, induce inverse micelle formation in phospholipid systems [342]. Other metal ions also result in this transformation (Fig. 4.47b) addition of adenosine triphosphate (ATP) removes the metal and leads to a reversion to the normal micellar pattern. Maas and Coleman [343] have postulated that such transitions may have significance in nerve membrane operation. Metal-ATP-phospholipid complexes... 

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