Adenosine-2 ,5-diphosphate pyrophosphate bond

The ATP molecule contains pyrophosphate linkages (bonds formed when two phosphate units are combined together) that release energy when needed. ATP can be hydrolyzed in two ways the removal of terminal phosphate to form adenosine diphosphate (ADP) and inorganic phosphate, or the removal of a terminal diphosphate to yield adenosine monophosphate (AMP) and pyrophosphate. The latter is usually cleaved further to yield two phosphates. This results in biosynthesis reactions, which do not occur alone, that can be driven in the direction of synthesis when the phosphate bonds are hydrolyzed. 

ATP is a nucleotide consisting of an adenine, a ribose, and a triphosphate unit (Figure 14.3). The active form of ATP is usually a complex of ATP with Mg2+ or Mn2+ (Section 9.4.2). In considering the role of ATP as an energy carrier, we can focus on its triphosphate moiety. ATP is an energy-rich molecule because its triphosphate unit contains two phosphoanhydride bonds. A large amount of free energy is liberated when ATP is hydrolyzed to adenosine diphosphate (ADP) and orthophosphate (Pj) or when ATP is hydrolyzed to adenosine monophosphate (AMP) and pyrophosphate... 

In these reactions, Pj stands for inorganic phosphate (P04 ) and PPj for inorganic pyrophosphate, two phosphate groups linked by a phosphodiester bond. As the top two reactions show, the removal of a phosphate or a pyrophosphate group from ATP leaves adenosine diphosphate (ADP) or adenosine monophosphate (AMP), respectively. 

It consists of the constituent mononucleotides, adenosine-5 -phosphate and nicotinamide mononucleotide, linked by a pyrophosphate bond. Splitting at the nicotinamide-ribose linkage yields nicotinamide and adenosine diphosphate ribose. This reaction is catalyzed by an enzyme from animal tissues and from Neurospora crassaJ The Neurospora enzyme appears in high concentration when the cells are grown on a zinc-deficient medium it has been purified from such material. The animal enzyme occurs in particles and has thus far not been solubilized. Both preparations are active with triphosphopyridine nucleotide (TPN), but reduced DPN is not split. 

The pyrophosphate bond of DPN is ruptured by an enzyme found in kidney particles and in potatoes. The potato enzyme has been purified over 750-fold and found also to cleave the pyrophosphate linkages of reduced DPN, TPN, flavinadenine dinucleotide, adenosine diphosphate, adenosine triphosphate, and thiamine pyrophosphate. 

Ci0HuN5O10P2- C4H12N03+ 2 H20 Adenosine 5 -[tris(hydroxy-methyl)methylammonium diphosphate], dihydrate (HMADPH)203 P2i Z = 2 Dx = 1.65 R = 0.047 for 1,624 reflections. The disposition of the base is anti (75.5°). The D-ribosyl group is T (183.0°, 35.4°) and the orientation about the exocyclic, C-4 - C-5 bond is gauche + (53.7 °). These features are similar to those of the favored conformations adopted by the nucleotide monophosphates. The pyrophosphate chain displays... 

Figure 3 Biosynthetic pathways. (A) In the terpenoid coupling reaction, isomers of isopentenyl pyrophosphate are joined with the loss of pyrophosphate, leading to a linear intermediate that is cyclized to a terpenoid skeleton, as shown for the diterpene taxol. (B) In the polysaccharide coupling reaction, hexose and pentose monomers are joined with the loss of a nucleoside diphosphate, as shown for the epivancosaminyl-glucose disaccharide of vancomycin. (C) In the first step of the nonribosomal peptide coupling reaction, an aminoacyl adenylate is transferred to a carrier protein or thiolation domain (denoted T ) with loss of adenosine monophosphate. In the second step, this carrier protein-tethered aminoacyl group is coupled to the amine of an aminoacyl cosubstrate, forming a peptide bond, as shown for two residues in backbone of vancomycin. (D) In the polyketide coupling reaction, the loss of carbon dioxide from a two or three-carbon monomer yields a thioester enolate that attacks a carrier protein-tethered intermediate, forming a carbon-carbon bond as shown for the polyketone precursor of enterocin.

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