Structure of the Arabinogalactan from Zea Shoots

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Abstract
The structure of the arabinogalactan obtained from the buffer-homogenate of Z. mays L. (hybrid B73 .times. Mo17) shoots was studied. The purified polysaccharide was investigated by methylation analysis before and after controlled acid hydrolysis. Arabinogalactan-1 consists of arabinose, galactose, xylose, uronic acid and glucose in the molar ratio of 37.1:55.8:3.0:4.1:trace and arabinogalactan-2 consists of the same sugars in the ratio of 35.4:53.9:1.6:9.2:trace. A trace of protein was detected in arabinogalactan-1 and about 0.2% was present in 2. About 20% of the galactose residues in arabinogalactan-1 constitute a (1 .fwdarw. 3)-linked galactan chain and .apprx. 60% constitute a (1 .fwdarw. 6)-linked galactan sequence. About 15% of the galactose residues in arabinogalactan-1 are substituted by galactose in the 3- and 6-positions, constituting branch points of the galactan framework. The remainder (5%) of the galactose residues in arabinogalactan-1 are located at nonreducing terminal positions. About 85% of the (1 .fwdarw. 6)-galactosyl sequence is substituted, mostly by single arabinose residues. Nonreducing terminal glucuronic acid is attached to C-6 of galactose residues. The basic structure of arabinogalactan-2 is similar to that of arabinogalactan-1.