Rabbit immune sera raised against denatured forms of horse liver alcohol dehydrogenase and of human ADH5 isozyme were found to react with the denatured subunits of all the human ADH isozymes regardless of their class.

The immune serum against the human ADH isozyme cross-reacted also with horse ADH subunits and, at appropriate dilutions, both the immune sera reacted with denatured yeast ADH, suggesting that common structures have been preserved in these molecules over a long evolutionary period.

The immune sera partially reacted also with the respective antigens in their native conformation, indicating that some ‘sequential ’ epitopes are expressed on the surface of the folded proteins.