The present invention provides a gene that codes for a protein, wherein the protein is an anthocyanin 5-O-glucosyltransferase, which is an enzyme that transfers a glycoside to the 5 position of a flavonoid. The disclosed anthocyanin 5-O-glucosyltransferases were isolated from Perilla fruescens, Verbena hybrida, Torenia hybrida, and Petunia hybrida. Also disclosed are genes that code for a protein having a modified amino acid sequence relative to the above amino acid sequence and having activity that transfers a glycoside to the 5 position of a flavonoid, and a process for producing the above protein using said gene. This gene can be used to artificially alter the color of plants.