Red mangos (Mangifera indica L.) accumulate appreciable amounts of cyanidin-based anthocyanins in the skin, and previous studies showed that these anthocyanins contain galactose as a sugar moiety. To date, two UDP:flavonoid 3-O-glycosyltransferase (UFGT)-like genes named MiUFGT1 and MiUFGT3 (MiUFGalT3) have been isolated from mango ‘Irwin’ peel as anthocyanin-related UFGT genes, but the function of the proteins of the genes have not yet been elucidated. In this study, we characterized recombinant MiUFGT1 and MiUFGalT3 expressed in Escherichia coli. In the presence of quercetin as an acceptor, rMiUFGT1 showed marginal glucosylation activity, while rMiUFGalT3 exhibited significant galactosylation activity 20-fold higher than its glucosylation activity. Specificity analysis using purified MiUFGalT3 found that rMiUFGalT3 almost equally accepts anthocyanidins and flavonols. The anthocyanins extracted from the ‘Irwin’ skins were cyanidin 3-O-galactoside and 7-O-methylcyanidin 3-O-galactoside by instrumental analyses, which is consistent with previous results obtained for other red mango cultivars. The results suggest that MiUFGalT3 is responsible for the red coloration of ‘Irwin’ mango fruit skins.

红芒果（Mangifera indica L.）在皮肤中积累了相当数量的基于花青素的花色苷，以前的研究表明这些花色苷含有半乳糖作为糖部分。迄今为止，已经从芒果'Irwin'果皮中分离出两个与花青素相关的UFGT基因，分别称为MiUFGT1和MiUFGT3（MiUFGalT3）的UDP：类黄酮3- O-糖基转移酶（UFGT）样基因，但是这些基因的蛋白质功能尚未阐明。在这项研究中，我们表征了在大肠杆菌中表达的重组MiUFGT1和MiUFGalT3。在槲皮素作为受体存在的情况下，rMiUFGT1显示出少量的糖基化活性，而rMiUFGalT3显示出显着的半乳糖基化活性，比其糖基化活性高20倍。使用纯化的MiUFGalT3进行的特异性分析发现，rMiUFGalT3几乎均等地接受花青素和黄酮醇。从“欧文”皮肤提取的花色素苷是矢车菊3- ö半乳糖苷和7- ö -methylcyanidin 3- ö半乳糖苷通过仪器分析，这与其它红色芒果栽培品种获得的先前结果一致。结果表明，MiUFGalT3引起“欧文”芒果果皮的红色。