This domain is found in the berberine bridge and berberine bridge- like enzymes which are involved in the biosynthesis of numerous isoquinoline alkaloids. They catalyse the transformation of the N-methyl group of (S)-reticuline into the C-8 berberine bridge carbon of (S)-scoulerine [1][2].

1: Molecular characterization of berberine bridge enzyme genes from opium poppy. Facchini PJ, Penzes C, Johnson AG, Bull D; Plant Physiol 1996;112:1669-1677. PMID:8972604

2: Characterization and mechanism of the berberine bridge enzyme, a covalently flavinylated oxidase of benzophenanthridine alkaloid biosynthesis in plants. Kutchan TM, Dittrich H; J Biol Chem 1995;270:24475-24481. PMID:7592663