Developmental changes of aldehyde dehydrogenase isozymes in human livers: mitochondrial ALDH2 isozyme is expressed in fetal livers.

Previous reports suggested that the major cytosolic aldehyde dehydrogenase (ALDH1) was present in fetal and infant livers, but the major mitochondrial isozyme (ALDH2) was absent or severely diminished. Re-examination by means of starch gel electrophoresis followed by enzyme activity staining, and by means of dot blot immuno-hybridization of liver samples with known genotypes of the ALDH2 locus, indicated that both ALDH1 and ALDH2 genes are expressed in fetal and infant livers. In addition, ALDH4 isozyme was also observed. The results imply that a fetus with the 'usual' homozygous ALDH1(2)/ALDH1(2) genotype, but not one with the atypical ALDH1(2)/ALDH2(2) or ALDH2(2)/ALDH2(2), is capable of detoxifying acetaldehyde transferred from the mother.