Cloning of a cDNA encoding a constitutively expressed rat liver cytosolic aldehyde dehydrogenase

The presence of a constitutively expressed aldehyde dehydrogenase (ALDH) in the rat liver cytosol is controversial (Tottmar et al., 1973; Lindahl and Evces, 1984; Berger and Weiner, 1977; Tank et al., 1981; Truesdale-Mahoney et al., 1981; Cao et al., 1989). A cDNA encoding a constitutively expressed rat liver cytosolic class 1 ALDH was cloned using a PCR-based strategy. The open reading frame consisted of 1503 nucleotides which encoded a protein of 501 amino acids. In order to compare the rat and human nucleotide sequences, we sequenced the entire open reading frame of a human liver cytosolic ALDH cDNA clone (Zheng et al., 1993). Rat liver constitutively expressed cytosolic ALDH was 99.7, 91.8, 89.0, and 83.8% identical to rat kidney, mouse liver, rat liver phenobarbital-inducible, and human liver cytosolic class 1 ALDH cDNAs, respectively. Northern blot analysis indicated that constitutively expressed rat cytosolic ALDH mRNA is expressed in lung, kidney, liver, skeletal muscle, and testis, with weak expression in heart and brain. These results strongly suggest that a constitutively expressed ALDH is present in rat liver cytosol.