Monoamine oxidase B, is a protein belongs to the flavin monoamine oxidase family. It is an enzyme located in the mitochondrial outer membrane. It catalyzes the oxidative deamination of biogenic and xenobiotic amines and plays an important role in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues. This protein preferentially degrades benzylamine and phenylethylamine.Edmondson et al. described structural features of the human enzyme: it has a hydrophobic bipartite elongated cavity that (for the "open" conformation) occupies a combined volume close to 700 Å3. hMAO-A has a single cavity that exhibits a rounder shape and is larger in volume than the "substrate cavity" of hMAO-B.