Sulfate group, transfer

The hydrolysis of sulfate monoesters has been studied increasingly in relation to sulfate group transfer in vivo. In general, the rate-enhancing effect on the sulfate cleavage is small even with hydroxamate- or imidazole-functionalized cationic micelles which are extremely effective for the hydrolysis of phenyl esters. Recently, Kunitake and Sakamoto (1979a) found that zwitterionic hydroxamate [47] cleaved 2,4-dinitrophenyl sulfate effectively in cationic and... 

Hopkins A, Day FLA, WUUams A. Sulfate group transfer between nitrogen and oxygen evidence consistent with an open exploded transition state. J Am Chem Soc. 1983 105 6062-6070. 

A breakthrough in 1990 was the identification of a phytohormone-like substance, called Nod Rm 1, from R. meliloti synthesized by gene products of /i JABC in the laboratory of Jean Denarie in Toulouse (29). The hsn genes nod H and nod Q were involved in the modification of this signal by transfer of a sulfate group... 

This class constitutes a large set of enzymes that catalyze the transfer of sulfate groups [EC 2.8.2.x]. See also specific enzyme... 

The tyrosine protein sulfotransferase preparations from Golgi-enriched membranes have been used for sulfation of synthetic mono- and multiple-tyrosine peptides related to known sulfation sites in proteins and peptides at analytical levels to establish the enzyme specificities.1f11-13] Preparative sulfations have not been carried out to date. A novel type of arylsulfotransferase produced by Eubacterium A-44 which is part of the human intestinal flora, has recently been discovered.1"1911111 This enzyme catalyzes the transfer of a sulfate group from phenolic sulfate, but not from 3 -phosphadenosine-5 -phosphasulfate, to other phenolic compounds. Using 4-nitrophenylsulfate as a donor substrate and tyrosine-containing peptides and proteins as acceptor substrates it catalyzes the specific sulfation of the tyrosine residues.11111-112 While this enzyme very efficiently sulfates tyrosine derivatives, the... 

A number of functional sialyl Lewis mimetics have been synthesized. Their activities in vitro are equal or even better than those of the tetrasac-charide itself. To overcome synthetic problems, efficient stereoselective glycosylations as well as new chemoenzymatic methods for C-C bond formations had to be developed. The substitution of neuraminic acid by (5)-phenyl- and (5)-cyclohexyl lactic acid, as less flexible glycol acid residues, turned out to be very successful [10]. Also, a phosphate and a sulfate group, respectively, mimic neuraminic acid without loss of activity [11]. (5)-Cyclohexyl lactic acid-mimetic 2 shows a more than ten-fold efficacy compared with sialyl Lewis, whereas the corresponding (/ )-isomer 3 is almost inactive [10]. The deviating orientation of the carboxylic acid functionality compared to the bioactive sialyl Lewis conformation leads to the examined loss of activity. It was shown by transfer-NOE measurements of the corresponding E-selectin complexes that the coordinates of the bioactive conformation of sialyl Lewis and of compound 2 are similar. Con.se-quently structure 2 should bind to E-selectin in the same manner as that of sialyl Lewis [ 10a, b]. 

Fig. 40. A proposed unified scheme of sulfate assimilation in algae. Adenylyl sulfate (APS) transfers the sulfo group via APS-sulfotransferase to form Car-S-SOr (Car = carrier), which is reduced further by thio-sulfonate reductase to Car-S-S which yields the thiol group of cysteine. In addition, if sulfite is released from Car-S-SOa (i.e., by thiol or from mutated sites) or if it enters the cell from outside, it can be reduced via a separate sulhte reductase. From Abrams and Schiff (57i).

Sulfate conjugation requires the prior activation of inorganic sulfate by adenosine triphosphate (ATP) to an active intermediate, 3 -phosphoadenosine-5-phosphosulfate (PAPSi. from which the sulfate group is transferred to a substrate (ROH). The final step is catalyzed by an enzyme called sulfotransferase. The three-step reaction sequence is illustrated in Figure 8.20. 

Figure 2.28. Coenzymes that are important in dmg metabolism. The groups transferred to the drags are shown in red. a UDP-glucuronide (transfers glucmonate), b PAPS (transfers sulfate), c S-adenosylmethionine (transfers methyl group).

SO is found in various vertebrate liver tissues and catalyzes the two-electron oxidation of sulfite to sulfate coupled to the reduction of two molecules of oxidized Cyt c. It contains molybdopterin and b-heme cofactors in separate domains connected by a polypeptide bridge, analogous to Fcyt b. The smaller N-terminal heme domain resembles cytochrome b the C-terminal domain contains Mo(VI) and catalyzes sulfite oxidation coupled to oxo group transfer. Two one-electron intramolecular ET steps, each followed by ET to Cyt c, complete the catalytic cycle. 

Baddiley et at. used the reagent to convert adenosine 3, 5 -diphosphate into adenosine 3 -phosphate-5 -sulfatophosphate. In the presence of an appropriate enzyme, this active sulfate transfers the sulfate group to a variety of substrates. 

Transferases catalyze the transfer of functional groups such as methyl, hydroxymethyl, formal, glycosyl, acyl, alkyl, phosphate, and sulfate groups by means of a nucleophilic substitution reaction. They are not widely used in industrial processes however, there are a few examples of industrial processes that utilize transferases. 

Conjugation of 0-, N- and S-contalnlng functional groups with sulfate Is very common In animal systems. Sulfate Is transferred from adenosine 3 -phosphate-5 -sulfatophosphate (PAPS) by a variety of transfer enzymes. The mechanisms for sulfation of xenobiotics (74,75) and the chemistry of sulfate esters and related compounds and the synthesis of these have been reviewed (75-77). Syntheses of 0-, N- and S-sulfate conjugates of xenobiotics may be carried out by the methods described below. 

The most common cerebrosides include galactosylceramide, glucosylceramide, and sulfatides (see Figure 19.14 for synthesis scheme). Sulfatides are made by transferring a sulfate group to a galactosylceramide (Figure 19.14). 

---