A pyridoxal-phosphate protein. The sulfur from free L-cysteine is first transferred to a cysteine residue in the active site, and then passed on to various other acceptors. The enzyme is involved in the biosynthesis of iron-sulfur clusters, thio-nucleosides in tRNA, thiamine, biotin, lipoate and pyranopterin (molybdopterin) . In Azotobacter vinelandii, this sulfur provides the inorganic sulfide required for nitrogenous metallocluster formation .
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SYSTEMATIC NAME
IUBMB Comments
L-cysteine:acceptor sulfurtransferase
A pyridoxal-phosphate protein. The sulfur from free L-cysteine is first transferred to a cysteine residue in the active site, and then passed on to various other acceptors. The enzyme is involved in the biosynthesis of iron-sulfur clusters, thio-nucleosides in tRNA, thiamine, biotin, lipoate and pyranopterin (molybdopterin) [2]. In Azotobacter vinelandii, this sulfur provides the inorganic sulfide required for nitrogenous metallocluster formation [1].
overall reaction, the enzyme shows a selenocysteine lyase activity approximately 280fold higher than its cysteine desulfurase activity. The desulfuration mechanism proposed for this enzyme seems to involve three different stages. At the beginning of the reaction, L-cysteine is quickly bound by the cofactor pyridoxal 5'-phosphate, shifting the UV-VIS spectrum of the enzyme. In this aldimine state, the L-cysteine sulfur atom is attacked by Cys384, resulting in persulfide formation. To regenerate the enzyme, this persulfide state must be resolved by transferring the sulphide to inorganic or organic acceptor molecules (accessory proteins, DTT or to other L-cysteine molecules)
0-0.5 M KCl gives optimal activities at around 55-60°C. When the KCl concentration is increased to 2.5-3 M, this optimum temperature shifts to between 70-75°C
activity is strongly dependent on the presence of dithiothreitol, with activity increasing up to 46% when the reductant is present in the reaction mixture. Concentrations higher than 5 mM cause an inhibitory effect
activity is strongly dependent on the presence of dithiothreitol, with activity increasing up to 46% when the reductant is present in the reaction mixture. Concentrations higher than 5 mM cause an inhibitory effect
0-0.5 M KCl gives optimal activities at around 55-60°C.When the KCl concentration is increased to 2.5-3 M, this optimum temperature shifts to between 70-75°C
0-0.5 M KCl gives optimal activities at around 55-60°C.When the KCl concentration is increased to 2.5-3 M, this optimum temperature shifts to between 70-75°C