Studies on the polysacharides from soy sauce. V. Detailed structure of an acidic polysaccharide in soy sauce, confirmed by use of two kinds of purified pectinases.

Abstract

The partially degraded polysaccharide obtained by means of mild acid hydrolysis of APS-I, an acidic polysaccharide in soy sauce, was incubated with an endo-polygalacturonase, and some acidic sugars liberated were fractionated and purified from the enzymatic hydrolyzate. They were identified as o-galacturonic acid (Gal A), its α-1, 4-linked dimer and trimer, D-xylose (Xyl) β1→3 Gal A and Xyl β1→3 Gal A α1→4 Gal A, and an acidic polymer composed of the above-mentioned sugars through methylation analysis and other methods. Methyl-esterized APS-I was subjected to β4-elimination with pectin lyase or by heat treatment. The high molecular fraction which was highly resistant to β-elimination, was concluded to be β-1, 4-linked D-galactan of which reducing-end group was attached to D-galacturonic acid. On the basis of these findings and previous knowledges, the construction of APS-I was also discussed.