PECTIC POLYSACCHARIDES IN COTYLEDONS OF KIDNEY BEANS

Pectic polysaccharides were extracted from cotyledons of kidney beans under conditions designed to prevent the degradation of pectic substances and separated into a fraction of neutral polysaccharides and those of weakly acidic pectinic acids containing 12.5 to 35.3% of galacturonic acid. Some of the latter fractions were hardly degraded by polygalacturonases, while the rest of the latter were susceptible to the same enzyme though the values of degradation limit were considerably low as compared with those of commercial pectic acids. It was found that polygalacturonase-resistant galacturonosyl residues in the molecules of the weakly acidic pectinic acids are partly esterified by methyl groups. Strongly acidic pectinic acid, the main component of cambium and callus tissue pectins, is probably absent erom the pectin of kidney bean cotyledons. In contrast, the neutral polysaccharide component is present in extraordinary large amount.