Enzyme | Class | Gene locus | Allelic Variant | Subunit composition |
K
m
(mM) |
V
max
(U/mg) | Vmax/Km (U/mg/mM) |
---|
ADH | I |
ADH1A
|  | αα | 5.2 | 0.24 | 0.047 |
 |  |
ADH1B
|
ADH1B*1
| β1β1 | 0.016 | 0.18 | 12 |
 |  |  |
ADH1B*2
| β2β2 | 1.9 | 4.8 | 2.6 |
 |  |  |
ADH1B*3
| β3β3 | 53 | 3.2 | 0.060 |
 |  |
ADH1C
|
ADH1C*1
| γ1γ1 | 0.11 | 0.81 |  |
 |  |  |
ADH1C*2
| γ2γ2 | 0.061 | 0.47 |  |
 | II |
ADH2
|  | ππ | 23 | 0.30 | 0.013 |
 | III |
ADH3
|  | χχ | 3,400 | 0.83 |  |
 | IV |
ADH4
|  | μμ(σσ) | 58 | 11 | 0.19 |
ALDH | I |
ALDH1A1
| Â | Tetramer | 0.033 | 0.63 | 19 |
 | II |
ALDH2
|
ALDH2*1
| Tetramer(E4) | 0.00020 | 0.60 | 3,000 |
 |  |  |
ALDH2*2
| Tetramer(K4) | 0.0046 | 0.017 | 3.6 |
- Enzyme activity was determined in 0.1M sodium phosphate, at pH 7.5 and 25°C. Samples contained 0.5 mM nicotinamide adenine dinucleotide (NAD; ie a cytosolic oxidised coenzyme concentration in hepatocytes), and various concentrations of ethanol for alcohol dehydrogenase (ADH) or of acetaldehyde for aldehyde dehydrogenase (ALDH). γ1γ1/γ2γ2 and χχ exhibit negative and positive cooperativity, respectively; hence they do not have a Km and the values shown are S0.5. Enzyme activity units (U) are expressed as micromoles NADH formed per minute under the assay conditions. Data are from Yin and Agarwal,[1] Yin et al [9]. and Lee et al [10].