A Novel, Easy Assay Method for Human Cysteine Sulfinic Acid Decarboxylase

Cysteine sulfinic acid decarboxylase catalyzes the last step of taurine biosynthesis in mammals, and belongs to the fold type I superfamily of pyridoxal-5′-phosphate (PLP)-dependent enzymes. Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in animal tissues; it is highly present in liver, kidney, muscle, and brain, and plays numerous biological and physiological roles. Despite the importance of taurine in human health, human cysteine sulfinic acid decarboxylase has been poorly characterized at the biochemical level, although its three-dimensional structure has been solved. In the present work, we have recombinantly expressed and purified human cysteine sulfinic acid decarboxylase, and applied a simple spectroscopic direct method based on circular dichroism to measure its enzymatic activity. This method gives a significant advantage in terms of simplicity and reduction of execution time with respect to previously used assays, and will facilitate future studies on the catalytic mechanism of the enzyme. We determined the kinetic constants using L-cysteine sulfinic acid as substrate, and also showed that human cysteine sulfinic acid decarboxylase is capable to catalyze the decarboxylation—besides its natural substrates L-cysteine sulfinic acid and L-cysteic acid—of L-aspartate and L-glutamate, although with much lower efficiency.

Efficient C3-alkylsulfenylation of indoles under mild conditions using Lewis acid-activated 8-quinolinethiosulfonates.

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>

Efficient C3-alkylsulfenylation of indoles under mild conditions using Lewis acid-activated 8-quinolinethiosulfonates.

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>

Recent Advances of Sulfonylation Reactions in Water

Background: The sulfonyl groups are general structural moieties present in agrochemicals, pharmaceuticals, and natural products. Recently, many efforts have been focused on developing efficient procedures for preparation of organic sulfones. Materials and Methods: Water, a proton source, is considered one of the most ideal and promising solvents in organic synthesis for its easy availability, low cost, nontoxic and nonflammable characteristics. From the green and sustainable point of view, more and more reactions are designed proceeding in water. Objective: The review focuses on recent advances of sulfonylation reactions proceeding in water. Sulfonylation reactions using sodium sulfinates, sulfonyl hydrazides, sulfinic acids, and sulfonyl chlorides as sulfonating agents were introduced in detail. Results and Discussion: In this review, sulfonylation reactions proceeding in water developed in recent four yields were presented. Sulfonylation reactions using water as solvent have attracted more and more attention because water is one of the most ideal and promising solvents in organic synthesis for its facile availability, low cost, nontoxic and nonflammable properties. Conclusion: Numerous sulfonating agents such as sodium sulfinates, sulfonyl hydrazides, sulfinic acid, sulfonyl chlorides and disulfides are efficient for sulfonylation reactions which proceed in water.

Lewis Acid-Activated 8-Quinolinethiosulfonates: An Efficient Methodology for CS(alkyl) Bond Formation

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>