Structural and biochemical insights into an anthocyanin-related glutathione transferase from bilberry and its inhibition by quercetin.
TL;DR
It is shown that the expression of arGST gene in bilberry increases during fruit ripening in parallel with other ABP genes and putative transcription factors and revealed a possible inhibitory effect of quercetin on arGST activity, as quercetin is a by-product of the anthocyanin biosynthetic pathway.
Abstract
The anthocyanin biosynthetic pathway (ABP), a branch of the phenylpropanoid pathway, is responsible for the production of a wide range of flavonoid compounds in plants. Anthocyanin-related glutathione transferases (arGSTs) have long been proposed to act as non-catalytic carrier proteins, mediating the vacuolar sequestration of anthocyanins. However, recent structural and biochemical evidence has suggested a potential catalytic role for arGSTs in the ABP, notably in catalyzing the dehydration of flavan-3,3,4-triol to anthocyanidin. Despite their importance, only a limited number of arGSTs have been characterized biochemically and structurally. Here, we investigated the arGST isoform from bilberry, one of the richest fruit sources of anthocyanins. We showed that the expression of arGST gene in bilberry increases during fruit ripening in parallel with other ABP genes and putative transcription factors. Biochemical and structural analyses highlighted the remarkable ability of GSTs to adapt to their substrates and revealed a possible inhibitory effect of quercetin on arGST activity, as quercetin is a by-product of the anthocyanin biosynthetic pathway.