Berberine bridge enzyme-like (BBE-like enzymes) form a subgroup of the superfamily of FAD-linked oxidases (SCOPe d.58.32), structurally characterized by a typical fold observed initially for vanillyl-alcohol oxidase (VAO). This proteins are part of a multigene family (PF08031) that can be found in plants, fungi and bacteria.
BBE-like enzymes family form a large subgroup that have a special C-terminal structural element adjacent to the substrate binding region. An homonym of this family is the (S)-reticuline oxidase or berberine bridge enzyme from California poppy (Eschscholzia californica), the responsible of catalyzing the conversion of (S)-reticuline to (S)-scoulerine. This conversion is made by an oxidative ring closure reaction. The product of this reaction is the C-C bond and is referred to as the berberine bridge. Also, marks a branch point in the biosynthesis of benzylisoquinoline alkaloids.
As mentioned above, BBE-like enzymes are in the large family of FAD-linked oxidases. Regarding the structure of this particular family, they have a FAD binding module formed by the N- and C- terminal parts of the protein. There is a substrate binding module that, in collaboration with isoalloxazine ring of FAD, disposes the environment for efficient substrate binding and oxidation.