**3.1. ALDH family members as stem cell markers**

ALDH proteins can be found in every subcellular region such as cytosol, endoplasmic reticulum, mitochondria, and the nucleus, with some even found in more than one location. ALDH isozymes found in organelles besides cytosol carry signal or leader sequences that make their translocation to specific subcellular regions possible. After translocation or import, while nuclear and microsomal signals remain intact, mitochondrial sequences might be removed (causing mature proteins to be shorter). Most of the ALDHs have a large tissue distribution and show distinct substrate specificity (Marchitti*, et al.*, 2008).
