IDENTIFICATION OF THE CLASS-3 ALDEHYDE DEHYDROGENASES PRESENT IN HUMAN MCF-7 0 BREAST ADENOCARCINOMA CELLS AND NORMAL HUMAN BREAST-TISSUE/

Affinity column chromatography was used to semipurify the very small a mounts of class-3 aldehyde dehydrogenase (ALDH-3) present in human MCF -7/0 breast adenocarcinoma cells and human normal breast tissue. Chara cterization of the semipurified enzymes revealed that each was a type- 1 ALDH-3 rather than a type-2 ALDH-3 as previously reported. Although clearly a type-1 ALDH-3, the MCF-7/0 enzyme, as well as the type-1 ALD H-3 constitutively present in cultured colon C cells and induced in cu ltured MCF-7/0 cells by methylcholanthrene, does, however, differ from the prototypical human stomach mucosa type-1 ALDH-3 in one, perhaps p harmacologically important, way, viz. when the ability to catalyse the oxidation of aldophosphamide is normalized by the ability to catalyse the oxidation of benzaldehyde, each of these enzymes, as well as the type-2 ALDH-3 found in MCF-7/OAP cells, exhibits greater ability to ca talyse the oxidation of aldophosphamide than does stomach mucosa type- 1 ALDH-3; hence, although not type-2 ALDH-3s, they may be slight varia nts of the prototypical type-1 ALDH-3.