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Lacourciere, GM and Stadtman, TC (1998) The NIFS protein can function as a selenide delivery protein in the biosynthesis of selenophosphate. J. Biol. Chem. 273:30921-6


The NIFS protein from Azobacter vinelandii is a pyridoxal phosphate-containing homodimer that catalyzes the formation of equimolar amounts of elemental sulfur and L-alanine from the substrate L-cysteine (Zheng, L., White, R. H., Cash, V. L., Jack, R. F., and Dean, D. R. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 2754-2758). A sulfur transfer role of NIFS in which the enzyme donates sulfur for iron sulfur center formation in nitrogenase was suggested. The fact that NIFS also can catalyze the decomposition of L-selenocysteine to elemental selenium and L-alanine suggested the possibility that this enzyme might serve as a selenide delivery protein for the in vitro biosynthesis of selenophosphate. In agreement with this hypothesis, we have shown that replacement of selenide with NIFS and L-selenocysteine in the in vitro selenophosphate synthetase assay results in an increased rate of formation of selenophosphate. These results thus support the view that a selenocysteine-specific enzyme similar to NIFS may be involved as an in vivo selenide delivery protein for selenophosphate biosynthesis. A kinetic characterization of the two NIFS catalyzed reactions carried out in the present study indicates that the enzyme favors L-cysteine as a substrate compared with its selenium analog. A specific activity for L-cysteine of 142 nmol/min/mg compared with 55 nmol/min/mg for L-selenocysteine was determined. This level of enzyme activity on the selenoamino acid substrate is adequate to deliver selenium to selenophosphate synthetase in the in vitro assay system described.




Azotobacter vinelandii/enzymology; Bacterial Proteins/antagonists & inhibitors; Bacterial Proteins/metabolism; Carbon-Sulfur Lyases; Drosophila Proteins; Lyases/antagonists & inhibitors; Models, Chemical; Nuclear Magnetic Resonance, Biomolecular; Phosphates/metabolism; Phosphorus Isotopes; Phosphotransferases/metabolism; Pyridoxal Phosphate; Selenium Compounds/metabolism; Selenocysteine/metabolism; Substrate Specificity



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status



GO:0031071: cysteine desulfurase activity

ECO:0000314: direct assay evidence used in manual assertion


Seeded From UniProt



GO:0031071: cysteine desulfurase activity



Figure 2 shows selenium elimination from L-selenocysteine by NifS.

CACAO 3370

See also


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