Publication details
Re-examination of the rationale for the use of bipyridylium cation radicals as site-specific electron donors for respiratory nitrate reduction
| Authors | |
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| Year of publication | 2008 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | Paracoccus denitrificans express two distinct nitrate reductases that are associated with the respiratory chain: the membrane-bound Nar, and the periplasmic Nap. Their activity is usually measured using colored bipyridylium cation radicals methyl viologen (MV) or benzyl viologen (BV) as electron donors. It is generally believed that the more polar MV does not enter the cell and hence donates electrons exclusively to Nap, while oxidation of hydrophobic BV reflects the action of both enzymes. This issue was further examined by a kinetic analysis of nitrate reduction in the wild-type strain and in the Nar or Nap mutant strains. The results show that (i) MV is a quite effective donor for either enzyme, (ii) BV blocks the active transport of nitrate to the active site of Nar, and (iii) BV functions as an ionophore for nitrate at higher concentrations. |
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