Biphenyl synthase () is an enzyme that catalyzes a biosynthesis of the polyketide, 3,5-dihydroxybiphenyl, from one unit of benzoyl-CoA and three of malonyl-CoA. It was characterised from the tree species Sorbus aucuparia and is part of the pathway that yields aucuparin, a phytoalexin.
This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is malonyl-CoA:benzoyl-CoA malonyltransferase. This enzyme is also called BIS.
References