Coffee bean arabinogalactans: acidic polymers covalently linked to protein.
The arabinogalactan content of green coffee beans (Coffea arabica var. Yellow Caturra) was released by a combination of chemical extraction and enzymatic hydrolysis of the mannan-cellulose component of the wall. Several arabinogalactan fractions were isolated, purified by gel-permeation and ion-exchange chromatography and characterised by compositional and linkage analysis. The AG fractions contained between 6 and 8% glucuronic acid, and gave a positive test for the beta-glucosyl-Yariv reagent, a stain specific for arabinogalactan-proteins. The protein component accounted for between 0.5 and 2.0% of the AGPs and contained between 7 and 12% hydroxyproline. The AG moieties displayed considerable heterogeneity with regard to their degree of arabinosylation and the extent and composition of their side-chains. They possessed a MW average of 650 kDa which ranged between 150 and 2000 kDa. An investigation of the structural features of the major AG fraction, released following enzymatic hydrolysis of the mannan-cellulose polymers, allowed a partial structure of coffee arabinogalactan to be proposed.
Redgwell
Robert J
RJ
Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, PO Box 44, CH-1000 26, Lausanne, Switzerland.
Curti
Delphine
D
Fischer
Monica
M
Nicolas
Pierre
P
Fay
Laurent B
LB
D000596:Amino Acids / Q000032:analysis; D002240:Carbohydrate Sequence; D003069:Coffee / Q000737:chemistry*; D005685:Galactans / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D006868:Hydrolysis; D009088:Mucoproteins / Q000737:chemistry* / Q000302:isolation & purification; D009844:Oligosaccharides / Q000737:chemistry; D019815:Oxalic Acid / Q000737:chemistry; D010940:Plant Proteins; D012995:Solubility; D013045:Species Specificity
D000596:Amino Acids; D003069:Coffee; D005685:Galactans; D009088:Mucoproteins; D009844:Oligosaccharides; D010940:Plant Proteins; C006619:arabinogalactan proteins; D019815:Oxalic Acid; D006026:Glycoside Hydrolases; C019713:alpha-N-arabinofuranosidase; C005653:arabinogalactan