RGD Reference Report - Role of extrahepatic alcohol dehydrogenase in rat ethanol metabolism. - Rat Genome Database

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Role of extrahepatic alcohol dehydrogenase in rat ethanol metabolism.

Authors: Boleda, MD  Julia, P  Moreno, A  Pares, X 
Citation: Boleda MD, etal., Arch Biochem Biophys 1989 Oct;274(1):74-81.
RGD ID: 1358222
Pubmed: PMID:2774584   (View Abstract at PubMed)

Rat alcohol dehydrogenase exhibits three isoenzymes with very different capacities of ethanol oxidation and with characteristic distribution in tissues. ADH-1 (class II isoenzyme, Km = 5 M) is especially concentrated in the most external organs: auditive, bucal, and nasal mucoses, cornea, esophagus, stomach, rectum, penis, and vagina. ADH-2 (class III isoenzyme) is present in all organs but has a poor activity with ethanol. ADH-3 (class I isoenzyme, Km = 1.4 mM) is the main liver isoenzyme, also present in lung, intestine, kidney, and sexual organs. At 33 mM ethanol and pH 7.5, total hepatic activity (3.5 +/- 0.6 units) represents 90% of the whole activity in the male rat, while the remaining 10% is distributed in many organs. The skin is the extrahepatic organ with the highest total activity (88 +/- 15 mU) followed by testis and small intestine. ADH-3 accounts for 96% of total activity (90% hepatic and 6% extrahepatic) and ADH-1 contributes with 4% (extrahepatic). However, in conditions that may be found in the digestive tract mucose after ethanol ingestion (pH 7.5, 1 M ethanol), stomach and small intestine activities represent 10% of the liver activity at 33 mM ethanol. Therefore, oral administration of ethanol will result in a higher contribution of the extrahepatic activity than will intravenous or intraperitoneal administration, because of the great ADH-1 content of the digestive tract. On the other hand, pyrazole inhibition constants at pH 7.5 for ADH-1 (33 mM) and ADH-3 (4.2 microM) are much higher than those at pH 10.0 (0.56 mM and 0.4 microM) and indicate that at the usual concentration of inhibitor only ADH-3 activity will be effectively suppressed. ADH-1 will be, therefore, responsible in part for the residual ethanol oxidation activity in pyrazole-treated rats.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
ethanol oxidation  IDA 1358222 RGD 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
alcohol dehydrogenase (NAD+) activity  IDA 1358222 RGD 
ethanol binding  IDA 1358222 RGD 
NAD binding  IDA 1358222 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Adh4  (alcohol dehydrogenase 4 (class II), pi polypeptide)

Additional Information