SCAO is an intracellular enzyme. Its common source are fungi and yeasts, but it has also been shown to be present in mollusks. It appears as an octameric protein, except for SCAO from
A. ochraceus, which has been shown to be a tetramer. Each of the subunites is 65-80 kDa. Nine SCAO isoforms have been found in
Ogataea methanolica, which has been shown to be a result of different combinations of two different subunits in the octamers, each coded by a different gene. ==Structural studies==