Strain | Specific activity (U/mg) |
---|
 | MDH | ME | LDH |
---|
Wild-type | 1.66 ± 0.088 | 0.30 ± 0.020 | < 0.007 |
Ccel_0137::LtrB (mdh) | 0.47 ± 0.056** | 0.25 ± 0.013* | ND |
Ccel_2485::LtrB (ldh) | 1.54 ± 0.36 | 0.29 ± 0.019 | NA |
(ldh mdh) | NA** | 0.44 ± 0.019** | < 0.055 |
- Mean and standard deviations of enzymatic specific activities are shown from at least three replicate assays. Continuous spectrophotometric assays were performed aerobically at ambient temperature (22°C), using 10 to 20 μg of protein sample in 1-ml reaction mixtures; 1 U of activity catalyzed the oxidation of 1 μmol of NAD(P)H per minute (MDH and LDH), or the reduction of 1 μmol of NADP+ per minute (ME). Specific activities were corrected for substrate-independent NAD(P)H oxidation. Malate dehydrogenase (MDH, EC 1.1.1.37) and malic enzyme (ME, EC 1.1.1.40) activities were measured as described in the Methods section, using NADH and NADP+ cofactors, respectively. No MDH activity was detected in the ldh mdh extracts (NA). Lactate dehydrogenase (LDH, EC 1.1.1.27) activity was determined as for MDH activity, using 1 mM pyruvate, 1 mM fructose-1,6-diphosphate and 0.2 mM NADH. No pyruvate-dependent NADH oxidation was detected in any sample: limits of detection are shown for wild-type and ldh mdh extracts.
- Values significantly different from wild-type activity (*P < 0.05; **P < 0.005) were calculated using analysis of variance (ANOVA).
- ND = not determined.