Distinct Substrate Specificity of Dihydroflavonol 4-Reductase from Flowers of Petunia hybrida

Dihydroflavonol 4-reductase from Petunia flowers cata­lyzes the reduction of dihydroquercetin to leucocyanidin and, in particular, of dihydromyricetin to leucodelphinidin, whereas reduction of the simple dihydroflavonol dihydro- kaempferol to leucopelargonidin could not be observed. This special substrate specificity of dihydroflavonol 4-re­ductase is most probably the reason for the observations that delphinidin derivatives are the main end products of anthocyanin biosynthesis in Petunia flowers, whereas an- thocyanins based on pelargonidin are rarely found and, if present, are only formed in very small amounts.