Class of enzymes
In enzymology, a cysteine desulfurase (EC 2.8.1.7) is an enzyme that catalyzes the chemical reaction
L-cysteine + [enzyme]-cysteine formula_1 L-alanine + [enzyme]-S-sulfanylcysteine
Thus, the two substrates of this enzyme are L-cysteine and [enzyme]-cysteine], whereas its two products are L-alanine and [enzyme]-S-sulfanylcysteine. One group of authors has given it the acronym hapE, for hydrogen sulfide, alanine, and pyruvate producing enzyme.
This enzyme belongs to the family of transferases, specifically the sulfurtransferases, which transfer sulfur-containing groups. The systematic name of this enzyme class is L-cysteine:[enzyme cysteine] sulfurtransferase. Other names in common use include IscS, NIFS, NifS, SufS, and cysteine desulfurylase. 
Function.
Bacteria contain cysteine desulfurases to form iron sulfur clusters in proteins.
However recently it has been shown that the enzyme, which produces hydrogen sulfide from cysteine, is also a virulence factor, namely for M.pneumoniae, in that it causes both α-hemolysis and β-haemolysis of red blood cells.
In mammals, the enzyme participates in thiamine metabolism.
Structural studies.
As of late 2007, only one structure had been solved for this class of enzymes, with the PDB accession code 1T3I.
References.
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