This family carries the region of the enzyme trans-2-enoyl-CoA reductase, at the very C-terminus, that binds to FAD. The activity was characterised in Euglena where an unusual fatty acid synthesis path-way in mitochondria performs a malonyl-CoA independent synthesis of fatty acids leading to accumulation of wax esters, which serve as the sink for electrons stemming from glycolytic ATP synthesis and pyruvate oxidation. The full enzyme catalyses the reduction of enoyl-CoA to acyl-CoA. The conserved region is seen as the motif FGFxxxxxDY [1].

1: Mitochondrial trans-2-enoyl-CoA reductase of wax ester fermentation from Euglena gracilis defines a new family of enzymes involved in lipid synthesis. Hoffmeister M, Piotrowski M, Nowitzki U, Martin W; J Biol Chem. 2005;280:4329-4338. PMID:15569691