Sulfuric Acid and L-Cysteine Derivatives

In addition to in the free state, sulfuric acid exists in nature in the form of esters, amides, and the anhydride with phosphoric acid  

Mixed anhydrides of sulfate and phosphory-lated compounds 

Sulfuric acid may be reduced to the level of sulfide and is then an important building stone of L-cysteine (see below). L-Cysteine, (S)- x-amino-/ -thiolpropionic acid, is one of the most important sulfur-containing substances in primary metabolism. The secondary products derived from L-cysteine may contain the sulfur in different states of oxidation. Of importance are sulfides (—S—), disulfides (—S—S— ), sulfenic acids (—S—OH), sulfoxides (—SO— ), sulfinic acids (—SO—OH) and sulfonic acids (—SO2—OH). 

Sulfuric acid esters with alcoholic or phenolic hydroxy groups, the mixed anhydrides adenosine-5 -sulfatophosphate and its 3 -phosphorylated derivative, as well as secondary products derived from L-cysteine occur in microorganisms, plants and animals. Sulfuric acid amides, e.g., the glucosinolates (D 9.4), are formed in certain plants. 

Inorganic sulfate is transformed to adenosine-5 -sulfatophosphate (ASP) and 3 -phosphate adenosine-5 -sulfatophosphate (PAPS, activated sulfate . Fig. 186) in microorganisms, plants, and animals. The sulfate group of ASP and PAPS may be reduced to the level of sulfide in microorganisms and plants. Carrier-bound sulfide reacts with 0-acetyl-L-serine or L-serine (D 10) to L-cysteine. 

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