Adenosine triphosphate , enzyme

Omeprazole is classified as a proton pump inhibitor, as it acts by blocking the hydrogen-potassium adenosine triphosphate enzyme system of the gastric parietal cells. Omeprazole therefore inhibits gastric acid release. Common side-effects associated with omeprazole include diarrhoea, headache, nausea and vomiting. Concurrent administration of omeprazole and phenytoin results in enhanced effects of phenytoin, which may lead to phenytoin toxicity. 

Calculation of Conformational Free Energies for a Model of a Bilobal Enzyme Protein kinases catalyze the transfer of phosphate from adenosine triphosphate (ATP) to protein substrates and are regulatory elements of most known pathways of signal transduction. 

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... 

Glucose [50-99-7] urea [57-13-6] (qv), and cholesterol [57-88-5] (see Steroids) are the substrates most frequentiy measured, although there are many more substrates or metaboUtes that are determined in clinical laboratories using enzymes. Co-enzymes such as adenosine triphosphate [56-65-5] (ATP) and nicotinamide adenine dinucleotide [53-84-9] in its oxidized (NAD" ) or reduced (NADH) [58-68-4] form can be considered substrates. Enzymatic analysis is covered in detail elsewhere (9). 

Active Transport. Maintenance of the appropriate concentrations of K" and Na" in the intra- and extracellular fluids involves active transport, ie, a process requiring energy (53). Sodium ion in the extracellular fluid (0.136—0.145 AfNa" ) diffuses passively and continuously into the intracellular fluid (<0.01 M Na" ) and must be removed. This sodium ion is pumped from the intracellular to the extracellular fluid, while K" is pumped from the extracellular (ca 0.004 M K" ) to the intracellular fluid (ca 0.14 M K" ) (53—55). The energy for these processes is provided by hydrolysis of adenosine triphosphate (ATP) and requires the enzyme Na" -K" ATPase, a membrane-bound enzyme which is widely distributed in the body. In some cells, eg, brain and kidney, 60—70 wt % of the ATP is used to maintain the required Na" -K" distribution. 

Molybdate is also known as an inhibitor of the important enzyme ATP sulfurylase where ATP is adenosine triphosphate, which activates sulfate for participation in biosynthetic pathways (56). The tetrahedral molybdate dianion, MoO , substitutes for the tetrahedral sulfate dianion, SO , and leads to futile cycling of the enzyme and total inhibition of sulfate activation. Molybdate is also a co-effector in the receptor for steroids (qv) in mammalian systems, a biochemical finding that may also have physiological implications (57). 

A good example of an affinity label for creatine kinase has been presented (35). This enzyme catalyzes the reversible transfer of a phosphoryl group from adenosine triphosphate [56-65-5] (17) to creatine [57-00-1] (18), leading to adenosine diphosphate [7584-99-8] (19) and phosphocreatine [67-07-2]... 

Thiamine can be considered to be the product of the quatemization of 4-methyl-5-(2-hydroxymethyl)thiazole (5) by an active derivative of 4-amino-5-(hydroxymethyl)-2-methyl pyrimidine (4) (Scheme 2). In living cells, pyramine can be activated by conversion into the diphosphate 7, via monophosphate 6, and the substrate of the enzyme responsible for the quatemization is not the thiamine thiazole, but its phosphate 8. The product of the condensation, thiamine phosphate (9), is finally converted into diphosphate 2—the biochemically active derivative—by hydrolysis to free thiamine, followed by diphosphorylation, or more directly, in some cases. Enzymes are known for all of the steps depicted in Scheme 2, and adenosine triphosphate (ATP) is, as usual, the phosphate donor. 

Nanninga, L.B. Mommaerts. C.R. (1960). Studies on the formation of an enzyme substrate complex between myosin and adenosine-triphosphate. Proc. Natl. Acad. Sci. USA 46, 1155-1166. 

Magnesium is the second most abundant intracellular cation. Magnesium serves as an essential cofactor for numerous enzymes and in many biochemical reactions, including reactions involving adenosine triphosphate (ATP).17 Magnesium disorders can be multifactorial and can be related to renal function, disease... 

Such enzymes catalyse the condensation of specific compounds, accompanied by the breakdown of a pyrophosphate bond in adenosine triphosphate (10.64). Adenosine is the condensation product of a pentose (D-ribofuranose) and a purine (adenine). Scheme 10.15 shows the action of glutamine synthetase on a mixture of L-glutamic acid (10.65) and... 

In the processes that require regeneration of cofactors such as nicotinamide adenine dinucleotide phosphate (NAD(P)H) and adenosine triphosphate (ATP), whole-cell biotransformations are more advantageous than enzymatic systems [12,15]. Whole cells also have a competitive edge over the isolated enzymes in complex conversions involving multiple enzymatic reactions [14]. 

The initial conversion of light into chemical energy takes place in the thylakoid membrane. Besides the chlorophylls and series of electron carriers, the thylakoid membrane also contains the enzyme adenosine triphosphate (ATP) synthase. The enzymes that are responsible for the actual fixation of C02 and the synthesis of carbohydrate reside in the stroma that surround the thylakoid membrane. The stroma also contains deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and ribosomes that are essential for protein synthesis [37]. 

Adenosine triphosphate (ATP) is one of the most important cofactors involved in many of the synthetic reactions going on within the cell. Its recent large scale in vitro enzymatic synthesis from adenosine and acetylphosphate is of particular interest. Three enzymes immobilized in polyacrylamide gel were used adenosine kinase, adenylate kinase and acetate kinase (lip. ... 

Another enzyme used for the measurement of glucose is hexokinase (EC 2.7.1.1) which catalyses the phosphorylation of glucose to produce glucose-6-phosphate with adenosine triphosphate as the phosphate donor and magnesium ions as an activator. The rate of formation of glucose-6-phosphate can be linked to the reduction of NADP by the enzyme glucose-6-phosphate dehydrogenase (EC 1.1.1.49). This indicator reaction can be monitored spectrophotometrically at 340 nm or fluorimetrically ... 

Phosphoribosylpyrophosphate (PRPP) synthetase is one of the very few enzymes which transfer a pyrophosphoryl group from ATP in one step. When the synthesis is carried out in lsO-enriched water, lsO is incorporated into the PRPP, but not into AMP.91 The lsO in the PRPP arises from a pre-exchange between the H2180 and the ribose phosphate, and hence the results confirm that fission of the /5-P—O bond takes place. PRPP and ATP are starting materials in the biosynthesis of histidine, and Ai-(5 -phospho-D-ribosyl)adenosine triphosphate (29) is an intermediate. The... 

Mitochondria produce energy through a process called oxidative phosphorylation. This process uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell s main energy source. A set of enzyme complexes, designated as complexes I-V, carry out oxidative phosphorylation within mitochondria. 

In some cases, enzymes require the assistance of coenzymes (cofactors) to ensure the reactions proceed. Coenzymes include vitamins, metal ions, acids, and bases. They can act as transporters or electron acceptors or be involved in oxidation-reduction reactions. At the completion of the reaction, coenzymes are released, and they do not form part of the products. For some reactions that are energetically unfavorable, an energy source provided by the compound adenosine triphosphate (ATP) is needed to ensure the reactions proceed, as shown in the following reactions ... 

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