Isolation ofH-alcohol dehydrogenase ofhumanliver: Isita determinant ofalcoholism? (ethanol metabolism/multiple molecular forms/affinity chromatography)

Humanliver alcohol dehydrogenase (alcohol: NAD+oxidoreductase, EC1.1.1.1), homogeneous byphysico- chemical criteria, hasbeenavailable inquantity only recently (Lange, L.G.V&M) topyrazole and its derivatives, which areusually potent ADHinhibitors (KI, 1 MM), aproperty that isthebasis fortheisolation ofII-ADH. The affinity resin 43-(N-6-aminocaproyl)aminopropyljpyrazole- Sepharose binds all other knownforms ofADHbutnotI1-ADH, thereby separating itselectively byaffinity chromatography. Inturn, this hasledtotheestablishment ofits identity with that enzyme formwhich waspreviously'known astheanodic band andcharacterized byahigh Kmforethanol (20mM atpH7.5). Theremarkable insensitivity ofII-ADH topyrazole inhibition hasalso permitted quantitation ofitsrole inhepatic ethanol oxidation. At5mM ethanol, asaturating concentration for vir- tually all other forms ofADH,II-ADH contributes less than 15% tototal ethanol oxidation. However, atintoxicating concen- trations, e.g., 60mM,itcanaccount for asmuchas40%ofthe total ethanol oxidation rateofliver, indicating aseemingly unique role forthis enzyme form inethanol elimination. Thus far, wehavefound theamount ofII-ADH varies fromliver to liver ofindividuals andisconsiderably morelabile thanthe other molecular forms, phenomena whose inter- orindepen- dence requires further study. Theisolation ofhuman11-ADH advances efforts torecognize andunderstand biochemical mechanisms that maybebiological determinants ofalcoholism andalcohol-related disease states, nowgenerally approached andmanaged largely aspsychosocial disorders.