Wednesday, November 26, 2008

Drunk Red Asians

Recently went drinking with a FOB (friend of the bayblab) and, as usual with him, he turned pretty red in the face. Apparently approximately half of people of Asian decent have this reaction to the consumption of alcohol, which has been nicknamed the "Asian glow".This glow shows up really well in this particular FOB, because he is half Caucasian, providing a pale, pastey canvas for his inebriated glow.
I had heard that the Asian glow was the result of a variant or deficit of the acetaldehyde dehydrogenase (ALDH2) enzyme. This enzyme is responsible for the conversion of acetaldehyde into acetic acid. Acetaldehyde is the first breakdown product of ethanol produced by alcohol dehydrogenase and it is this nasty compound that causes all of the "Asain glow" symptoms which also include: nausea, headaches, light-headedness, an increased pulse, occasional extreme drowsiness, and occasional skin swelling and itchiness. It is also responsible for the scurge of mankind; the hangover.
Worse still for the previously mentioned FOB is that the east asian drunken red face variant of ALDH2 is associated with increased risk of alcoholism related cancer. This is likely because acetaldehyde is carcinogenic and would be in increased concentrations if you posses a less active ALDH2 enzyme.
If you're smart and paying attention you'd remember that the FOB is of both Asian and Caucasian decent. So what about his Caucasian allele? How could an enzyme deficiency be domninant? Well, the origonal paper on the subject explain demonstrates that ALDH2 exists as a homotetramer and that the Asian allele has a markedly reduced half-life and in a cell expressing both versions of the subunit passes on it's reduced stability to the resulting heterotetrameric complex. So presumably the increased acetaldehyde is not due to decreased specific activity of ALDH2 in some Asians but due to lower stability of the active enzyme complex. Therefore this allele is dominant.