A method of epimerizing an (S)-1-benzylisoquinoline alkaloid to an (R)-1-benzylisoquinoline alkaloid is provided. The method comprises contacting the (S)-1-benzylisoquinoline alkaloid with at least one enzyme. Contacting the (S)-1-benzylisoquinoline alkaloid with the at least one enzyme converts the (S)-1-benzylisoquinoline alkaloid to an (R)-1-benzylisoquinoline alkaloid.