InterPro domain: IPR010970

Cysteine desulfurases are pyridoxal-phosphate enzymes which catalyse the removal of sulphur from L-cysteine to form L-alanine and elemental sulphur. These enzymes have been shown to play an important role in the biosynthesis of iron-sulphur clusters, thionucleosides in tRNA, thiamine, biotin, lipoate and molydopterin [ 1 ].

This entry represents a subfamily of NifS-related cysteine desulfurases that are often involved in iron-sulphur cluster formation, which is needed for nitrogen fixation and other vital functions [ 2 ]. Many of these enzymes, in addition to cysteine desulfurase activity, also show selenocysteine lyase activity where L-selenocysteine is converted to L-alanine and selenide [ 3 ]. Some of these enzymes are much more specific for selenocysteine than cysteine and are thus believed to function in selenium metabolism rather than sulphur metabolism.

Structural studies of the Escherichia coli [ 4 ] and Synechocystis [ 5 ] enzymes indicate that they are homodimers which show a similar fold to other members of the alpha family of pyridoxal-phosphate enzymes [ 6 ].

1. Bacterial cysteine desulfurases: their function and mechanisms. Appl. Microbiol. Biotechnol. 60, 12-23
2. Incorporation of iron-sulphur clusters in membrane-bound proteins. Biochem. Soc. Trans. 29, 418-21
3. A nifS-like gene, csdB, encodes an Escherichia coli counterpart of mammalian selenocysteine lyase. Gene cloning, purification, characterization and preliminary x-ray crystallographic studies. J. Biol. Chem. 274, 14768-72
4. Analysis of the E. coli NifS CsdB protein at 2.0 A reveals the structural basis for perselenide and persulfide intermediate formation. J. Mol. Biol. 315, 1199-208
5. Kinetic and structural characterization of Slr0077/SufS, the essential cysteine desulfurase from Synechocystis sp. PCC 6803. Biochemistry 43, 12210-9
6. Structure, evolution and action of vitamin B6-dependent enzymes. Curr. Opin. Struct. Biol. 8, 759-69