The anthocyanidin compounds cyanidin, delphinidin, peonidin and to a lesser extent pelargonidin can act as substrates. The enzyme does not catalyse glucosylation of the 5-position of cyanidin and does not act on flavanols such as quercetin and kaempferol (cf. EC 2.4.1.91 flavonol 3-O-glucosyltransferase). In conjunction with EC 1.14.20.4, anthocyanidin oxygenase, it is involved in the conversion of leucoanthocyanidin into anthocyanidin 3-glucoside. It may act on the pseudobase precursor of the anthocyanidin rather than on the anthocyanidin itself [3].