Adenosine triphosphate yields

Acidic solutions (pH 1—5) of copper(n)-adenosine triphosphate yield ultrasonic attenuation spectra consisting of three maxima. The overall reaction which fits the data best is... 

FIGURE 16 7 Nucleophilic substitution at the primary carbon of adenosine triphosphate (ATP) by the sulfur atom of methionine yields S adenosylmethionme (SAM) The reaction is catalyzed by an enzyme... 

By this method adenosine triphosphate (ATP) and inosine triphosphate (ITP) were prepared in 89% and 93% yield, respectively 51]... 

Other nuclei, such as 13C or 31P, may be used to study other metabolite pools, or they can complement H-NMR to create more sophisticated NMR spectra. 13C-NMR provides a greater spectral range ( 200 ppm) than H-NMR ( 15 ppm). Although lower natural abundance of 13C (1.1%) yields lower sensitivity, it also provides an opportunity to use isotopic enrichment to trace specific metabolic pathways with enhanced sensitivity.4 31P can observe high-energy phosphate metabolites such as adenosine triphosphate. 

For most amino acids, the ester linkage between the ct-COOH group of the amino acid and the 3 -terminal adenosine of a cognate tRNA is formed in a two-step mechanism catalyzed by an aminoacyl-tRNA synthetase (aaRS). ° In this so-called direct pathway, the aaRS first catalyzes the reaction of the amino acid with adenosine triphosphate (ATP), yielding the enzyme-bound high-energy intermediate aa AMP and PPi in the second step, this aaRS-bound intermediate reacts with tRNA to yield aa-tRNA and AMP (Figure 1). 

As an example of enzyme action, look in Figure 24.11 at the enzyme hexose kinase, which catalyzes the reaction of adenosine triphosphate (ATP) with glucose to yield glucose-6-phosphate and adenosine diphosphate (ADP). The enzyme first binds a molecule of ATP cofactor at a position near the active site, and glucose then bonds to the active site with its C6 hydroxyl group held rigidly in position next to the ATP molecule. Reaction ensues, and the two products are released from the enzyme. 

Fats, carbohydrates, and proteins are metabolized in the body to yield acetyl CoA, which is further degraded in the citric acid cycle to yield two molecules of CO2 plus a large amount of energy. The energy output of the various steps in the citric acid cycle is coupled to the electron-transport chain, a series of enzyme-catalyzed reactions whose ultimate purpose is to synthesize adenosine triphosphate (ATP). 

Some of the reactions of PO3- parallel enzymatic reactions promoted by adenosine triphosphate (ATP). Pyruvate kinase catalyzes the equilibration of ATP and pyruvate with adenosine diphosphate (ADP) and phosphoenol pyruvate (11,12). In a formal sense, this reaction resembles the preparations of enol phosphate (eqs. 6 and 7). Cytidine triphosphate synthetase catalyzes the reaction of uridine triphosphate with ammonia to yield cytidine triphosphate (13). In a formal sense, this reaction resembles the replacement of the ester carbonyl group of ethyl acetate by the nitrogen of aniline (eq. 8). 

Storage of norepinephrine in vesicles Dopamine is transported into synaptic vesicles by an amine transporter system that is also involved in the re-uptake of preformed norepinephrine. This carrier system is blocked by reserpine (see p. 78). Dopamine is hydroxylated to form norepinephrine by the enzyme, dopamine 3-hydroxylase. Synaptic vesicles contain dopamine or norepinephrine plus adenosine triphosphate and the 3-hydroxylase. Not all of the norepinephrine is packaged in vesicles some exists in a cytoplasmic pool that can be displaced. In the adrenal medulla, norepinephrine is methylated to yield epinephrine both are stored in chromaffin cells. On stimulation, the adrenal medulla releases about 85% epinephrine and 15% norepinephrine. 

Firefly luciferase catalyzes the reaction of adenosine triphosphate and a substituted benzothiazole luciferin. The quantum yield of the reaction is high and therefore measurement of the enzyme offers good sensitivity. Coupling of luciferase to other molecules is a problem because there is a highly reactive amino group in the active site that must be protected from reaction with coupling rei ents (36, 37). 

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