<P> A study was conducted in order to find a correlation between allelic distribution and alcoholism, and the results suggest that the allelic distribution arose along with rice cultivation in the region between 12,000 and 6,000 years ago . In regions where rice was cultivated, rice was also fermented into ethanol . The results of increased alcohol availability led to alcoholism and abuse by those able to acquire it, resulting in lower reproductive fitness . Those with the variant allele have little tolerance for alcohol, thus lowering chance of dependence and abuse . The hypothesis posits that those individuals with the Histidine variant enzyme were sensitive enough to the effects of alcohol that differential reproductive success arose and the corresponding alleles were passed through the generations . </P> <P> Classical Darwinian evolution would act to select against the detrimental form of the enzyme (Arg variant) because of the lowered reproductive success of individuals carrying the allele . The result would be a higher frequency of the allele responsible for the His - variant enzyme in regions that had been under selective pressure the longest . The distribution and frequency of the His variant follows the spread of rice cultivation to inland regions of Asia, with higher frequencies of the His variant in regions that have cultivated rice the longest . The geographic distribution of the alleles seems to therefore be a result of natural selection against individuals with lower reproductive success, namely, those who carried the Arg variant allele and were more susceptible to alcoholism . </P> <P> The first - ever isolated alcohol dehydrogenase (ADH) was purified in 1937 from Saccharomyces cerevisiae (brewer's yeast). Many aspects of the catalytic mechanism for the horse liver ADH enzyme were investigated by Hugo Theorell and coworkers . ADH was also one of the first oligomeric enzymes that had its amino acid sequence and three - dimensional structure determined . </P> <P> In early 1960, it was discovered in fruit flies of the genus Drosophila . </P>

Where is alcohol dehydrogenase found in the cell