The enzymatic activity of AC has been proposed as a potential endophenotype for alcohol dependence. AC is responsible for the conversion of adenosine 5′-triphosphate (ATP) to the second messenger cAMP88,89 Other major components involved in AC/cAMP pathway are various extracellular signal receptors and heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) that couple the signals generated at receptors to the catalysis of cAMP formation. Nine isoforms of the mammalian AC enzyme (types I - IX), with differing regulatory properties, are known to exist.88,90
