The periplasmic nitrate reductase ofRhodobacter capsulatus; purification, characterisation and distinction from a single reductase for trimethylamine-N-oxide, dimethylsulphoxide and chlorate
✍ Scribed by A. G. McEwan; H. G. Wetzstein; O. Meyer; J. B. Jackson; S. J. Ferguson
- Publisher
- Springer
- Year
- 1987
- Tongue
- English
- Weight
- 784 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0302-8933
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✦ Synopsis
The periplasmic dissimilatory nitrate reductase from Rhodobacter capsulatus N22DNAR + has been purified. It comprises a single type of polypeptide chain with subunit molecular weight 90,000 and does not contain heme. Chlorate is not an alternative substrate. A molybdenum cofactor, of the pterin type found in both nitrate reductases and molybdoenzymes from various sources, is present in nitrate reductase from R. capsulatus at an approximate stoichiometry of 1 molecule per polypeptide chain. This is the first report of the occurrence of the cofactor in a periplasmic enzyme. Trimethylamine-N-oxide reductase activity was fractionated by ion exchange chromatography of periplasmic proteins. The fractionated material was active towards dimethylsulphoxide, chlorate and methionine sulphoxide, but not nitrate. A catalytic polypeptide of molecular weight 46,000 was identified by staining for trimethylamine-N-oxide reductase activity after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The same polypeptide also stained for dimethylsulphoxide reductase activity which indicates that trimethylamine-N-oxide and dimethylsulphoxide share a common reductase.