Cadmium-detoxification in the earthworm Enchytraeus: specific expression of a putative aldehyde dehydrogenase.

The ubiquitous earthworm Enchytraeus buchholzi is provided with a very effective, but still unknown, mechanism of Cadmium (Cd)-detoxification, a central role in which has been ascribed to the Cd-inducible crp-gene encoding a novel cysteine-rich, non-metallothionein 25 kDa protein. This study identifies another Cd-responsive gene by differential screening of a cDNA-library constructed from Cd-exposed E. buchholzi. The isolated cDNA-clone designated Ebaldh encodes a putative aldehyde dehydrogenase. Northern blot analysis shows that the Ebaldh-expression is strongly enhanced by Cd, but remains unaffected by other stressors such as Zn, Hg, and H2O2. This Cd-specificity of Ebaldh suggests that Cd-detoxification in E. buchholzi requires low intracellular concentrations of aldehydes which are known to target sulfhydryl groups thus inactivating the Cd-binding capacity of CRP.