PMID:9812986

Citation	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
Abstract	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.
Links	PubMed
Keywords	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
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
AZOVI:NIFS	enables	GO:0031071: cysteine desulfurase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
AZOVI:NIFS		GO:0031071: cysteine desulfurase activity	ECO:0000314:		F		Figure 2 shows selenium elimination from L-selenocysteine by NifS.	complete CACAO 3370

References

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