Schematic illustration of phylogenetic relationships among ALDH families. The phylogenetic tree was constructed using the Clustal W and PHYLIP programs. An asterisk indicates an ALDH with HDH activity. ALDH, aldehyde dehydrogenase; BALDH, betaine aldehyde dehydrogenase; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GGSALDH, γ-glutamyl semialdehyde dehydrogenase; MMSALDH, methylmalonyl semialdehyde dehydrogenase; SSALDH, succinic semialdehyde dehydrogenase.