Isolation of a lectin binding rhamnogalacturonan-I containing pectic polysaccharide from pumpkin

Jing Zhao; Fuming Zhang; Xinyue Liu; Kalib St Ange; Anqiang Zhang; Quanhong Li; Robert J Linhardt

doi:10.1016/j.carbpol.2017.01.067

Isolation of a lectin binding rhamnogalacturonan-I containing pectic polysaccharide from pumpkin

Carbohydr Polym. 2017 May 1:163:330-336. doi: 10.1016/j.carbpol.2017.01.067. Epub 2017 Jan 21.

Authors

Jing Zhao¹, Fuming Zhang², Xinyue Liu³, Kalib St Ange³, Anqiang Zhang³, Quanhong Li⁴, Robert J Linhardt⁵

Affiliations

¹ College of Food Science & Nutritional Engineering, China Agricultural University, Beijing, 100083, China; China National Engineering Research Center for Fruit and Vegetable Processing, Beijing 100083, China; Key Laboratory of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China; Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
² Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
³ Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
⁴ College of Food Science & Nutritional Engineering, China Agricultural University, Beijing, 100083, China; China National Engineering Research Center for Fruit and Vegetable Processing, Beijing 100083, China; Key Laboratory of Fruit and Vegetable Processing, Ministry of Agriculture, Beijing 100083, China. Electronic address: quanhong_li@hotmail.com.
⁵ Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA; Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA; Departments of Biology and Biomedical Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. Electronic address: linhar@rpi.edu.

PMID: 28267513
DOI: 10.1016/j.carbpol.2017.01.067

Abstract

A rhamnogalacturonan-I (RG-I) containing pectic polysaccharide (PPc) was isolated from pumpkin following a low-temperature alkali treatment and a combination of gradual alcohol precipitation and ion-exchange. Monosaccharide compositional analysis of PPc revealed the presence of rhamnose, galacturonic acid, galactose, and arabinose in a molar ratio of 7.4: 25: 28: 2.6. Structural and linkage analysis by 1D NMR (¹H NMR and ¹³C NMR), and 2D NMR (COSY, TOCSY, HSQC, and elevated temperature HMBC) suggested that PPc was a RG-I-like pectic polysaccharide, branched at the C-4 of some of the (about 29% of) rhamnosyl units, with relatively long β-1,4-d-galactan side chains to which were attached, through the C-3 of β-d-Gal, terminal non reducing α-Araf units. The results of surface plasmon resonance (SPR) show that PPc binds to two types of lectin, Ricinus communis agglutinin 120 (RCA₁₂₀) and Galectin-3 (Gal-3). These binding studies show quick association and slow dissociation with a moderate binding affinity between PPc and Gal-3 of 1.26μM. The interaction between PPc and Gal-3 suggest the potential use of pumpkin pectic polysaccharide as a Gal-3 inhibitor in functional food or drug development applications.

Keywords: Lectin; NMR; Pectin; Pumpkin residues; Rhamnogalacturonan-I.

MeSH terms

Cucurbita / chemistry*
Galactans
Magnetic Resonance Spectroscopy
Monosaccharides
Pectins / chemistry*
Pectins / isolation & purification
Polysaccharides / chemistry*

Substances

Galactans
Monosaccharides
Polysaccharides
Pectins