The CDTA-soluble pectic substances from soybean meal are composed of rhamnogalacturonan and xylogalacturonan but not homogalacturonan

Structural characteristics of pectic substances extracted from soybean meal cell walls (water unextractable solids) with a chelating agent-containing buffer (0.05M 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) and 0.05M NH4-oxalate in 0.05M NaOAc buffer) were studied The arabinogalactans present as side chains to the rhamnogalacturonan backbone were largely remo ved by enzymatic hydrolysis using endo-galactanase, exo-galactanase, endo-a rabinanase, and arabinofuranosidase B. The remaining pectic backbone appear ed to be resistant to enzymatic degradation by pectolytic enzymes. After pa rtial acid hydrolysis of the isolated pectic backbone, one oligomeric and t wo polymeric populations were obtained by size-exclusion chromatography. Mo nosaccharide and linkage analyses, enzymatic degradation. and NMR spertrosc opy of these populations showed that the pectic substances in the original extract contain both rhamnogalacturonan and xylogalacturonan regions, while homogalacturonan is absent. (C) 2001 John Wiley & Sons, Inc.