Adenosine 5 -phosphosulfate, formation

Adenosine 3 -monophosphate, trans-hydrogenase and, 71 Adenosine 3, 5-monophosphate, trans-hydrogenase and, 71 Adenosine S -phosphosulfate, formation of, 279... 

Figure 9.141 Time course of formation of adenosine 5 -phosphosulfate (APS) by activity in rat liver. The reaction mixture contained, in a final volume of 350 /xL, 30 ju.mol of Tris-HCl (pH 8.0), 0.9 /xmol of ATP, 3 /unol of magnesium sulfate, 6 /xmol of sodium fluoride, and 50 fiL of inorganic pyrophosphatase (2.5 U). A50/xL supernatant sample (19 mg of protein) from rat liver was added to start the reaction. Then samples were removed at intervals, and the reaction was terminated and analyzed. Chromatograms were obtained after incubation for (A) 0 minutes, (B) 15 minutes, and (C) 45 minutes. Arrow indicates elution time for the reaction product APS. (From Mina and Rossomando, 1988.)...

A.7.1 Esterification of Acids using Carbodiimides. The formation of anhydrides from carboxylic acids, thiocarboxylic acids, sulfonic acids and phosphorous acids are discussed in Section 2.4.S.2. In this section only special cases of anhydride formation are described. Mixed anhydrides of amino acids and adenylic acid are produced from the corresponding acids using DCC as the condensation agent. ° Mixed anhydrides not containing amino acids, such as butyryl adenate, adenosine 5 -phosphosulfate and p-nitrophenyl-thymidine-5-phosphate are also obtained. 

Fig. 31.41 The sulfoconjugation reaction example of 4-nitrophenol as acceptor substrate. Step 1, PAPS formation from adenosine 5 -phosphosulfate (APS) step 2, sulfate conjugation with the subsequent release of 3 -phosphoadenosine 5 -phosphate (PAP) step 3, possible hydrolysis of the sulfoconjugate by arylsulfatases.

A pathway first outlined in detail by Davies et al. (1966) has been examined in a number of tissues. Davies et al. (1966) used Euglena gracilis and showed that cysteic acid could act as a precursor of the sulfolipid. Incorporation from 801 was reduced in the presence of molybdate, which was thought to implicate adenosine-3 -phosphate 5 -phosphosulfate (PAPS). As a result of these experiments (see Table II), Davies et al. (1966) suggested a pathway involving formation of the sulfonic acid grouping by the reaction of PAPS with phosphoenolpyruvate. This reaction would be followed by a number of interconversions and, finally, by an aldol condensation with dihy-droxyacetone phosphate. 

M. are synthesized from the UDP-Af-acetylhexos-amine and UDP-n-glucuronic (or iduronic) add. Sulfate is transferred directly from adenosine-3 -phos-phate-5 -phosphosulfate after formation of the polysaccharide chain. Synthesis takes place in the endoplasmic reticulum. 

Sulfate activation formation of the active sulfates, Phosphoadenosinephosphosulhite (see), (PAK) and adenosine S -phosphosulfate (APS). PAPS is the substrate of sulfotransferases in the synthesis of sulfate esters. APS is the substrate of sulfate assimilation and sulfate respiration. 

Conjugation of phenols, aliphatic and steroid alcohols with sulfate occurs in mammals, birds, reptiles, amphibia, but not in fish. In addition, active sulfate in the presence of transferase will conjugate aromatic amines and form sulfamates [70] in mammals, birds, and spiders. The synthesis of sulfate derivatives occurs in the soluble fraction of liver homogenates through the formation of adenosine-5 -phosphosulfate (APS) and 3 -phosphoadenosine-5 -phosphosulfate (PAPS) [21]. The reactions may be written as follows ... 

The enzymic reactions responsible for anhydride synthesis are reversible, and in some cases such as in DPN S3rnthesis, the equilibrium constant is close to unity (387). There are, however, several mechanisms by which formation of a nucleotide acid anhydride can be encouraged, and its destruction by the reverse reaction prevented. This may be illustrated in the synthesis of adenosine-5 -phosphosulfate (APS) which takes place by a reversible reaction that strongly favors its destruction [Eq. (77)] (334)... 

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