Biochemical and Functional Characterization of Anthocyanidin Reductase (ANR) from Mangifera indica L.

Lin Tan,Farrukh Azeem,Youfa Kang,Zhaoxi Zhou,Ikhlas Khan,Decai Tuo,Mei Wang,Lina María Preciado Rojo,Zhiqiang Pan

doi:10.3390/molecules23112876

Abstract

Mango (Mangifera indica L.) is abundant in proanthocyanidins (PAs) that are important for human health and plant response to abiotic stresses. However, the molecular mechanisms involved in PA biosynthesis still need to be elucidated. Anthocyanidin reductase (ANR) catalyzes a key step in PA biosynthesis. In this study, three ANR cDNAs (MiANR1-1,1-2,1-3) were isolated from mango, and expressed in Escherichia coli. In vitro enzyme assay showed MiANR proteins convert cyanidin to their corresponding flavan-3-ols, such as (−)-catechin and (−)-epicatechin. Despite high amino acid similarity, the recombinant ANR proteins exhibited differences in enzyme kinetics and cosubstrate preference. MiANR1-2 and MiANR1-3 have the same optimum pH of 4.0 in citrate buffer, while the optimum pH for MiANR1-1 is pH 3.0 in phosphate buffer. MiANR1-1 does not use either NADPH or NADH as co-substrate while MiANR1-2/1-3 use only NADPH as co-substrate. MiANR1-2 has the highest Km and Vmax for cyanidin, followed by MiANR1-3 and MiANR1-1. The overexpression of MiANRs in ban mutant reconstructed the biosynthetic pathway of PAs in the seed coat. These data demonstrate MiANRs can form the ANR pathway, leading to the formation of two types of isomeric flavan-3-ols and PAs in mango.

Highlights

IntroductionIntroductionProanthocyanidins or PAs ( known as condensed condensed tannin) belong to a subclass of plant metabolites called called flavonoids. flavonoids.WhenWhenincorporated incorporated into diet, PAs improve human health into thethe diet, PAs cancan improve human health via via anticancer, anti-oxidant, cardiovascular protection and immunomodulatory [1,2,3,4,5,6,7].theirtheir anticancer, anti-oxidant, cardiovascular protection and immunomodulatory effectseffects [1,2,3,4,5,6,7]
A high conservation was found at the glycine-rich Rossmann dinucleotide (NADPH/NADH)-binding domain (G-G-X-G-X-X-A) in these 17 homologs (Figure 2)
Theprotein protein sequence derived from three clones contained specificity sequence derived from thethe three clones contained the conserved Rossmann dinucleotide-binding domain amino-termini (G-G-X-G-X-X-A), which is responsible for binding nucleotide cofactors [53]

Summary

Introduction

IntroductionProanthocyanidins or PAs ( known as condensed condensed tannin) belong to a subclass of plant metabolites called called flavonoids. flavonoids.WhenWhenincorporated incorporated into diet, PAs improve human health into thethe diet, PAs cancan improve human health via via anticancer, anti-oxidant, cardiovascular protection and immunomodulatory [1,2,3,4,5,6,7].theirtheir anticancer, anti-oxidant, cardiovascular protection and immunomodulatory effectseffects [1,2,3,4,5,6,7]. Whenincorporated incorporated into diet, PAs improve human health into thethe diet, PAs cancan improve human health via via anticancer, anti-oxidant, cardiovascular protection and immunomodulatory [1,2,3,4,5,6,7]. These metabolites are widely distributed in stems, flowers, roots, tea-leaves, seedcoats coatsand andfruits fruits [8,9,10,11,12,13,14]. Metabolites are widely distributed in stems, flowers, roots, tea-leaves, seed. PAs play an important role in plant response to biotic/abiotic stresses like herbivore damage, fungal. PAs play an important role in plant response to biotic/abiotic infection, mechanical wounding and ultraviolet irradiation [15,16]. PAs can affect plant traits of commercial interest, including skin color [17,18]

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