Table 1.
Enzymatic properties of archaeal and bacterial copper-containing nitrite reductase (NirK). ND; not determined.
| Organisms | MW* (kDa) | Cu content† (atom per subunit) | Absorption (nm) | Activity‡ Turnover (s−1) |
Km (μM) | Reference |
|---|---|---|---|---|---|---|
| Archaeal NirK | ||||||
| Nitrososphaera viennensis | 105±1.5 | 2.9 | 590 | |||
| NO2− reduction | 3.1 | 287 | This study | |||
| NH2OH oxidation | 0.039 | 97 | This study | |||
| Bacterial NirK (NO2− reduction) | ||||||
| Nitrosomonas europaea | 96 | ND | 450, 597 | 288 | ND | 18 |
| Nitrosococcus oceani | 114 | 1.67 | 455, 575 | 1,600 | 52 | 16 |
| Achromobacter xylosoxidans | 110 | 1.99 | 595 | 172 | 35 | 14, 32 |
| Candidatus Jettenia caeni | 101 | ND | 449, 598 | 319 | 250 | 7 |
*
Molecular weight (MW) of a trimeric NirK. The MW of Ca. Jettenia caeni NirK was calculated from amino acid sequences without a signal peptide sequence.
†
Copper contents previously assessed by chemical analyses were shown.
‡
The following electron donors were used to evaluate the turnover number of NO2− reduction; methyl viologen for N. europaea and Nc. oceani, pseudoazurine for A. xylosoxidans, and benzyl viologen for Ns. viennensis and Ca. Jettenia caeni NirK.