Distribution and possible metabolic role of class III alcohol dehydrogenase in the human brain

In human brain, the sole alcohol dehydrogenase (ADH) present in significant quantity has been shown to be Class III (χ) ADH and this ADH is ineffective in generating potentially toxic and reactive acetaldehyde from ethanol at concentrations attainable in living brain tissue. We have extended this finding to show that Class I ADH potentially present is undetectable even when concentrated several hundred-fold. Purified Class III ADH from human brain is identical in its pattern of tryptic peptides and in other properties to Class III ADH from human liver. Immunohistochemical staining and western immunoblots using polyclonal antibodies reveal that Class III ADH is widely distributed in brain and most concentrated in the subependymal layer and perivascular areas. Class III ADH closely resembles ω-hydroxyfatty acid dehydrogenase and a possible role for the brain enzyme is in the oxidization of long chain fatty alcohols and ω-hydroxyfatty acids.