The NIFS Protein Can Function as a Selenide Delivery Protein in the Biosynthesis of Selenophosphate
| Autor: | Gerard M. Lacourciere, Thressa C. Stadtman |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Lyases
chemistry.chemical_element Biochemistry Phosphates Substrate Specificity chemistry.chemical_compound Selenocysteine lyase Bacterial Proteins Biosynthesis Selenide Drosophila Proteins Selenium Compounds Nuclear Magnetic Resonance Biomolecular Molecular Biology Pyridoxal chemistry.chemical_classification Azotobacter vinelandii biology Phosphotransferases Phosphorus Isotopes Substrate (chemistry) Cell Biology Enzyme assay Selenocysteine Carbon-Sulfur Lyases Enzyme Models Chemical chemistry Pyridoxal Phosphate biology.protein Selenium |
| Zdroj: | Journal of Biological Chemistry. 273:30921-30926 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.273.47.30921 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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