Enzymatic activity of atypical Oriental types of aldehyde dehydrogenases.

Catalytic activity of the atypical Oriental-type aldehyde dehydrogenase-2 (ALDH2) was considered to be null or severely diminished. Recently it was suggested that the atypical ALDH2(2) retained about 30% of the specific activity of the usual ALDH2(1). We reexamined the problem by two-dimensional crossed immunoelectrophoresis. The usual Caucasian livers exhibited two distinctive precipitin peaks, one corresponding to the cytosolic ALDH1 and the other corresponding to the usual mitochondrial ALDH2(1), in both protein stain and enzyme activity stain. In contrast, the atypical Oriental livers exhibited two precipitin peaks in protein stain, but only one peak, corresponding to ALDH1, in enzyme activity stain. These results support the original notion that the atypical ALDH2(2) is enzymatically inactive or far less active than the usual enzyme, refuting the idea of the atypical ALDH2(2) with substantial enzyme activity.