The enzyme, characterized from the cyanobacterium?Nostoc punctiforme?PCC 73102, is involved in the biosynthesis of the sunscreen compound shinorine. It requires a divalent metal ion (Zn2+?or Co2+) and an NAD+?cofactor, which is transiently reduced during the reaction.?cf. EC?4.2.3.152, 2-epi-5-epi-valiolone synthase and EC?4.2.3.155, 2-epi-valiolone synthase.