Table 1. Kinetic Parameters for NADH Oxidation Catalyzed by NDH-2 from Soluble and Overexpressed Membrane Preparations with Various Electron Acceptorsa.
| [NADH] varied | [quinone] varied | ratio plot | |
|---|---|---|---|
| NDH-2 Overexpressed Membranes with UQ0 | |||
| KMNADH (mM) | 0.24 ± 0.07b | 0.32 ± 0.15 | – |
| KMUQ0 (mM) | 0.64 ± 0.20 | 0.23 ± 0.10 | – |
| kcat (s–1) | 580.0 ± 170 | 570.0 ± 200 | 330 ± 15 |
| Soluble NDH-2 with UQ0 | |||
| KMNADH (mM) | 0.14 ± 0.02 | 0.12 ± 0.2 | – |
| KMUQ0 (mM) | 0.58 ± 0.11 | 0.35 ± 0.5 | – |
| kcat (s–1) | 480.0 ± 60 | 425.0 ± 35 | 390 ± 70 |
| Soluble NDH-2 with UQ1 | |||
| KMNADH (mM) | ndc | ndc | 0.13d |
| KMUQ1 (mM) | ndc | ndc | 0.050 ± 0.02e |
| kcat (s–1) | ndc | ndc | 500.0 ± 50 |
| Soluble NDH-2 with UQ2 | |||
| KMNADH (mM) | 0.12 ± 0.2 | ndc | 0.12 |
| KMUQ2 (mM) | <0.02 | ndc | 0.051 ± 0.05 |
| kcat (s–1) | 640.0 ± 40 | ndc | 1150.0 ± 350 |
| Soluble NDH-2 with Menadione | |||
| KMNADH (mM) | ndc | 0.23 ± 0.01 | 0.23 |
| KMmenadione (mM) | ndc | 0.10 ± 0.01 | 0.04 ± 0.02 |
| kcat (s–1) | ndc | 423.0 ± 70 | 400.0 ± 25 |
a
Kinetic constants determined by global fitting using eq 4 in Experimental Procedures.
b
Errors are standard errors from fits or propagation errors calculated from fitted values when division of errors was necessary.
c
Not determined.
d
The KM value is the average for NADH with UQ0 and UQ2.
e
KM calculated according to eq 2 assuming KM for NADH where KMUQ1 = α(slope × Vmax – KMNADH).