Table 1.
Alcohol dehydrogenase (Adh) Class 1-V and Aldh isozymes in humans and rats.
| Enzyme class | Isozymes in humans | Human expression sites | Rat expression sites | Sexually dimorphic expression M vs. F | Metabolic parameter | Reference |
|---|---|---|---|---|---|---|
| ADH | Ethanol Km (mM), Vmax (min-1) | |||||
| Class I | ADH1A ADH1B∗1, ADHB∗2, ADH1B∗3, ADH1C∗1, ADH1C∗2 | Liver (all) and stomach (ADH1C∗1) | Duodenum, colon, rectum, liver, kidney, stomach, greatest expression in the above tissues vs. other ADH classes. | Higher in female rats’ liver Lower in female rats’ gastrointestinal tract |
4.0, 30 0.05, 4 0.9, 350 40.0, 300 1.0, 90 0.6, 40 |
Estonius et al., 1993; Aasmoe and Aarbakke, 1999; Westerlund et al., 2007 |
| ADH2 | ADH4 | Liver | Liver, kidney, stomach, duodenum | Lower in female rats’ liver | 30, 20 | Estonius et al., 1993; Aasmoe and Aarbakke, 1999 |
| ADH3 | ADH5 | Most tissues | Tongue, esophagus, stomach, duodenum, jejunum, Ileum, colon, rectum, liver, kidney, stomach | None | >1000, 100 | Estonius et al., 1993; Westerlund et al., 2007 |
| ADH4 | ADH7 | Gastric mucosa | Tongue, esophagus, stomach | ? | 30, 1800 | Westerlund et al., 2007 |
| ADH5 | ADH6 | Liver, stomach | ? | ?. ? | ||
| ALDH (9 classes, but 3 major in rats) | Disulfiram IC50 of acetaldehyde metabolism (uM) | Quertemont, 2004 | ||||
| ALDH1 (RalDH) | None | Cytosolic (high Km for acetaldehyde) | Tongue, esophagus, stomach, duodenum, jejunum, not detectible in liver | ? | Human 0.15 Rat0.10 |
Keung and Vallee, 1993; Chen et al., 1996; Westerlund et al., 2007; Koppaka et al., 2012 |
| ALDH2 | None | Mitochondria (Low Km for acetaldehyde) | Liver | ? | Human 1.45 Rat >20 |
Keung and Vallee, 1993; Koppaka et al., 2012 |
| ALDH3 | Constitutive, xenobiotic inducible | GI tract | ? | ? | Lindahl, 1992; Xie et al., 1996 |