TABLE 3.
Succinate:acceptor oxidoreductasesa
| Parameter | S. acidocaldarius (DSM 639) | Sulfolobus sp. strain 7 |
|---|---|---|
| No. of subunits | 4 | 4 |
| Mr (103) | 138 | 148 |
| Mr subunits (103) | 66, 31, 28, 12.8 | 66, 37, 33, 12 |
| Genes | sdhABCD | NA |
| Flavin (nmol/mg) | 4.6 | 5.6 |
| λmax (nm) | 455 (ox-red) | 445 |
| Fe (nmol/mg) | 102 | 83 |
| S0 (nmol/mg) | 150 | — |
| Cyt b | None | None |
| Km (succinate) (mM) | 1.4 | 0.28 |
| Km (DCPIP) (μM) | 65.4 | 89 |
| Km (Qcal) (μM) | — | 60 |
| Vmax (μmol/min/mg)b | 7.8 (55°C) | 13 (50°C) |
| — | 14 (Q1) | |
| — | 1.8 (Qcal) | |
| Turnover (s−1) | 154 (81°C) | — |
| EPR | ||
| (S-3) oxidized | g = 2.02 | g = 2.02 |
| g = 2.08 (satell.) | — | |
| (S-1) succinate reduced | gz = 2.05 | gz = 2.03 |
| gy = 1.935 | gy = 1.94 | |
| gx = 1.904 | gx = 1.90 | |
| pH optimum | 6.5 | 6.5–6.8 |
| Ea (kJ/mol) | 59–64 | — |
| Ki | ||
| Malonate (mM) | 3.1 | — |
| Oxaloacetate (mM) | 0.28 | — |
| TCBQc (μM) | 1.5 | — |
a
Comparison of structural and kinetic data for the only two archaeal SDH preparations (complex II). Data were taken from references 250, 369, and 371. NA, not available; Qcal, caldariella quinone; Q1, ubiquinol-1; (satell.), satellite band; —, not tested or not reported.
b
Activity with artificial electron acceptors phenazine methosulfate (PMS) and 2,6-dichlorophenolindophenol (DCPIP).
c
TCBQ, tetrachlorobenzoquinone.