Adenosine 3 -phosphate, structure

Figure 2 Details of two successive trans-esterification reactions. In the first step, the 2 -OH group of the branch point adenosine nucleophilically attacks the phosphate at the junction of the S exon and intron (S splice site), resulting in the formation of a new S -2 phosphodiester bond between the first nucleotide of the intron and the branch point adenosine (lariat structure formation) and breakage of an old 3 -S phosphodiester bond between the last nucleotide of the S exon and the first nucleotide of the intron (cut-off S exon formation). In the second step, the 3 -OH group of the cut-off S exon nucleophilically attacks the phosphate at the junction of the intron and 3 exon, ligating the two exons (mRNA formation) and releasing the lariat intron. The phosphates at the S splice site (red) and at the 3 splice site (green) and the branch point adenosine and its 2 -OH group are pictured. The lines represent the intron and boxes depict exons (El and E2).

Compounds that serve as energy carriers for the chemotrophs, linking catabolic and biosynthetic phases of metabolism, are adenosine phosphate and reduced pyridine nucleotides (such as nicotinamide dinucleotide or NAD). The structure of adenosine triphosphate (ATP) is shown in Fig. 1. It contains two energy-rich bonds, which upon hydrolysis, yield nearly eight kcal/mole for each bond broken. ATP is thus reduced to the diphosphate (ADP) or the monophosphate (AMP) form. 

A possible explanation for these results is shown in Fig. 11. Normally, the 2 -hydroxyl is hydrogen bonded to both His-51 and Ser-48. Note that these residues occur in the middle of a sequence that is intimately involved with defining the active site. When acyclo-NAD is bound, these residues can relocate to the position formerly occupied by the 2 -hydroxyl. The attendant movement of the protein backbone would be transmitted into the active site via Cys-46 and His-67, which are directly coordinated to the catalytic zinc, and Asp-49, which is hydrogen bonded to His-67. Arg-47, the counterion for the adenosine phosphate, and Val-57, part of the substrate binding pocket, could also participate in the structural reorganization. The sterically demanding secondary alcohols would then be more affected by conformational changes in the active site than the primary alcohols. ... 

In addition to these we need to mention a small group of metabolites that belong structurally with the building blocks of nucleic acids but which have major metabolic functions that are quite separate from their relationship to nucleic acids. These are the adenosine phosphates two of these, adenosine 5 -triphosphate and adenosine 5 -diphosphate, participate in many metabolic reactions (more, indeed, than any other substance, aside from water) a third, adenosine 5 -monophosphate, participates in relatively few reactions but affects many enzymes as an inhibitor or as an activator. These names are cumbersome for everyday use and biochemists refer to them nearly aU of the time as ATP, ADP, and AMP, respectively. In animals, the ATP needed for driving all the functions of the cell is generated in small compartments of cells called mitochondria. For the purposes of this book we shall not need to know any details of how mitochondria fulfill their functions, but we do need to know that they exist, because we shall meet them again in a quite different context it turns out that in most organisms mitochondria contain small amounts of their own DNA, and this allows some special kinds of analyses. Adenosine, the skeleton from which ATP, ADP, and AMP are built, has a separate importance as one of the four bases that define the sequence of DNA. 

Conformation of Guanosine and Adenosine Phosphates in Small-Molecule and Ligand/Protein Crystal Structures... 

Adenylic Acid. Muscle adenylic acid ergaden -ylic acid t -adenylic acid adenosine S -monophosphate adenosine phosphate adenosine-5 -phosphoric add edeno-sine-5. monophosphoric acid A5MP AMP NSC-20264 Addiyl Cardiomone (Na salt) Lycedan My -B-Den My-oston Phosaden. C,0HhNjO7P mol wt 347.23, C 34.59%, H 4.06%, N 20.17%, O 32,25%, P 8,92%. Nucleotide widely distributed in nature. Prepn from tissues Embden, Zimmerman, Z. Physrot Chem. 167, 137 (1927) Embden, Schmidt, ibid. 181, 130 (1929) cf. Kalckar, J. B.ol Chem. 167, 445 (1947). Prepn by hydrolysis of ATP with barium hydroxide Kerr, 3. Biot Chem. 139, 13l (1941). Synthesis Baddiley, Todd. 3. Chem. Soc. 1947, 648. Commercial prepn by enzymatic phosphorylation of adenosine. Monograph on synthesis of nucleotides G. R. Pettit. Synthetic Nucleotides vol, 1 (Van Nostrand-Reinhold. New York, 1972) 252 pp. Crystal structure Kraut, lensen, Acta Cryst 16, 79 (1963). Reviews see Adenosine Nucleic Acids. 

Solvation and Shift Reagents.—The solvation parameters for a series of alcohols have been determined using the n.m.r. chemical shift of tris-n-butylphosphine oxide. Ion pair association between tetraphenylboron and cationic centres was used to study the electronic structure of aminonaphthylphosphonium salts (24 X = Ph4B ). Shift reagents have been used in the conformational analysis of adenosine phosphates and aromatic solvent induced shifts to probe the stereochemistry of butadienylphosphonates and their polymers. The geometries of difluorophosphine derivatives were evaluated from liquid crystal n.m.r. studies with the aid of electron diffraction. ... 

Addison s disease see Adrenal corticosteroids. Adenine 6-aminopurine (Fig.), one of the common nucleic acid bases. An A. residue is also present in the structure of the adenosine phosphates and other physiologically active substances, including Ni-... 

Fig.2. Adenosine phosphates. Synthesis of cyclic adenosine 3, 5 - monophosphate (cAMP), and the structure of cyclic A. O -dibutyryladenosine y.B -monophosphate.

Structure of Coemyme A. The elucidation of the structure of CoA depended heavily on d radation by specific enzymes. The phosphate on carbon 3 of the adenosine was shown to be a monoester phosphate by hydrolysis with prostate phosphomonoesterase. The localization of the monoester at the 3 position was established by its sensitivity to a b nucleotidase that attacks only nucleoside 3 -pbosphates, not 2 - or 5 -phosphates. The original CoA molecule or the phosphatase product, depbospho CoA, can be split by nucleotide pyrophosphatases from potato or snake venom. These reactions permitted the identification of the adenosine phosphate portion of the molecule. The position of the phosphate on pantothenic acid cannot be determined enzymatically, but was established by studies on the synthesis of CoA from synthetic phos-phorylated pantetheines. Pantetheine is split to thiolethanolamine and pantothenic acid by an enzyme found in liver and kidney. This enzyme also attacks larger molecules, including CoA. 

Thioanalogues of adenosine phosphates have been studied by n.m.r. and the chemical shifts were compared to those of the oxygenated compounds. The effects of changing pH and the concentration of added Mg + led to the conclusion that chemical shift data cannot yield unequivocal information concerning the absolute structure of the metal complexes of nucleosides but can be used to monitor changes in chelation, for example, in binding to enzymes. ... 

The structure and formation of ATP. (A) The chemical structure of adenosine triphosphate (ATP). "C" indicates carbon, "N" nitrogen, "O" oxygen, "H" hydrogen and "P" phosphorus. Note the negative charges on the phosphate groups (PO3 ). (B) ATP can be formed from adenosine diphosphate (ADP). 

Draw the structure of cyclic adenosine monophosphate (cAMP), a messenger involved in the regulation of glucose production in the body. Cyclic AMP has a phosphate ring connecting the 3 and 5 hydroxyl groups on adenosine. 

Cyclic adenosine monophosphate (cyclic AMP), a modulator of hormone action, is related to AMP (Problem 29.24) but has its phosphate group linked to two hydroxyl groups at C3 and C5 of the sugar. Draw the structure of cyclic AMP. 

Phosphate also plays a central role in the transmission and control of chemical energy within the cells primarily via the hydrolysis of the terminal phosphate ester bond of the adenosine triphosphate (ATP) molecule (Fig. 14-3b). In addition, phosphate is a necessary constituent of phospholipids, which are important components in cell membranes, and as mentioned before, of apatite, which forms structural body parts such as teeth and bones. It is not surprising, therefore, that the cycling of P is closely linked with biological processes. This connection is, in fact, inseparable as organisms cannot exist without P, and their existence controls, to a large extent, the natural distribution of P. 

---