RESUMO
The chemical structure of pea pectin was delineated using pectin-degrading enzymes and biochemical methods. The molecular weight of the pea pectin preparation was 488,000, with 50 % arabinose content, and neutral sugar side chains attached to approximately 60 % of the rhamnose residues in rhamnogalacturonan-I (RG-I). Arabinan, an RG-I side chain, was highly branched, and the main chain was comprised of α-1,5-l-arabinan. Galactose and galactooligosaccharides were attached to approximately 35 % of the rhamnose residues in RG-I. Long chain ß-1,4-galactan was also present. The xylose substitution rate in xylogalacturonan (XGA) was 63 %. The molar ratio of RG-I/homogalacturonan (HG)/XGA in the backbone of the pea pectin was approximately 3:3:4. When considering neutral sugar side chain content (arabinose, galactose, and xylose), the molar ratio of RG-I/HG/XGA regions in the pea pectin was 7:1:2. These data will help understand the properties of pea pectin.
Assuntos
Estrutura Molecular , Pectinas/química , Pisum sativum/química , Arabinose/química , Galactanos/química , Galactose/química , Glicosídeo Hidrolases/química , Ácidos Hexurônicos/química , Pisum sativum/ultraestrutura , Pectinas/ultraestrutura , Polissacarídeos/química , Ramnose/química , Xilose/químicaRESUMO
An arabinogalactan-protein (WSSP-AGP) was isolated from the tuberous cortex of the white-skinned sweet potato (WSSP; Ipomoea batatas L.). It consists of 95% (w/w) carbohydrate and 5% (w/w) protein with high contents of hydroxyproline, alanine, and serine. Its sugar composition is α-L-Rha:α-L-Ara:ß-D-Gal:ß-D-GlcA in a molar ratio of 1.0:4.1:7.6:1.3. Its weight-average molecular weight was estimated to be 126,800 g/mol by high-performance size exclusion chromatography coupled with multiangle laser light scattering. Structural analysis indicated that WSSP-AGP is a (1â3)-ß-D-galactan highly branched at O-6 with (1â6)-ß-D-galactan, in which the branched chains are substituted at the O-3 position with α-L-Araf-(1â and α-L-Araf-(1â5)-α-L-Araf-(1â and at the O-6 position typically with α-L-Rhap-(1â4)-ß-D-GlcAp-(1â as terminating groups. Continuous administration of WSSP-AGP to KKAy mice significantly lowered fasting plasma glucose levels. This indicates that WSSP-AGP plays an important role in the hypoglycemic effects of WSSP.