Table 1.
Protein | Source | Purification conditions | Vmax [U (mg protein)-1] | Km (mM) | Metals per heterodimer* |
UreA2B2 | H. mustelae nikR ureB | Aerobic (O2) | NA† (10.7 ± 0.4) | NA† | ICP: 2.3 Fe, 0.2 Zn; PA: 2.01 ± 0.05 Fe |
UreA2B2 | H. mustelae nikR ureB | EDTA, O2 | NA† | NA† | ICP: 2.3 Fe, 0.2 Zn |
UreA2B2 | H. mustelae nikR ureB | BP‡, O2 | NA† | NA† | ICP: 1.9 Fe, 0.1 Zn |
UreA2B2 | H. mustelae nikR ureB | Anaerobic | 14.0 ± 0.2 | 1.6 ± 0.1 | ICP: 1.1 Fe, 0.7 Zn; PA: 1.05 ± 0.07 Fe |
UreA2B2 | E. coli pEC015 | O2 | NA†(9.8 ± 0.5) | NA† | ICP: 1.0 Fe, < 0.1 Zn; PA: 1.13 ± 0.12 Fe |
UreA2B2 | E. coli pEC015 | EDTA, βME, O2 | NA† | NA† | ICP: 0.8 Fe, < 0.1 Zn; PA: 0.89 ± 0.02 Fe |
UreAB | H. mustelae wild-type | EDTA, βME, O2 | 390 ± 6 | 1.7 ± 0.1 | ICP: 0.6 Ni, 0.2 Fe, < 0.1 Zn |
UreAB | H. mustelae nikR ureB2 | EDTA, βME, O2 | 840 ± 20 | 2.3 ± 0.2 | ICP: 1.1 Ni |
*Measured by ICP-AES (ICP) or based on reactivity with 1,10-phenanthroline (PA, average of triplicate experiments ± standard deviation).
†Not active; numbers in parentheses are specific activities of samples after reductive activation for 80 min.
‡Treated with 2,2-bipyridyl and dithionite prior to aerobic purification.