Table 1.

Two east Asian genetic variants that alter alcohol metabolism

		ALDH2 gene	ADH1B gene
Enzyme*		ALDH2, an aldehyde dehydrogenase	ADH1, an alcohol dehydrogenase
Enzyme function		Acetaldehyde breakdown, by oxidation to acetate	Alcohol breakdown, by oxidation to acetaldehyde
Description of variants
	SNP identifier	rs671	rs1229984
	Nucleotide change	G→A	G→A
	Amino acid change†	Glu504→Lys	Arg48→His
	Enzyme activity change	Decreased substantially	Increased substantially
	Alcohol clearance rate	Unaffected	Accelerated
	Acetaldehyde clearance rate	Decreased substantially	Unaffected
	Alcohol intake	Reduced substantially	Reduced‡

ALDH=aldehyde dehydrogenase. ADH=alcohol dehydrogenase. SNP=single nucleotide polymorphism.

^*ALDH2 is a tetramer of the ALDH2 gene product that requires all four parts to be functional, so a loss-of-function variant is nearly dominant. ADH1 is a dimer that requires two functional parts from the products of any of three similar genes, ADH1A, ADH1B, and ADH1C.

^†For ALDH2 and ADH1B, each of these amino acid changes can be described as altering the “*1” into the “*2” enzyme isoform.

^‡The ADH1B-rs1229984 east Asian variant is nearly dominant, with AA and AG having similar effects on alcohol intake.