Isolation of D-galacturonic acid 1-phosphate from hydrolysates of cell wall lipopolysaccharide extracted from Xanthomonas campestris.

d-Galacturonic acid 1-phosphate was found to be one of the products formed during hydrolysis of the cell wall lipopolysaccharide of Xanthomonas campestris in 0.01 n acetic acid at pH 3.3. The molecule was shown to consist of equimolar amounts of d-galacturonic acid and phosphate. Resistance to borohydride reduction before, but not after, treatment with Escherichia coli alkaline phosphatase indicated that the phosphate group is attached to carbon-1 of the galacturonic acid. The presence of an additional phosphate group in the heteropolysaccharide of the cell wall lipopolysaccharide was also demonstrated. This phosphate group was considerably more resistant to acid hydrolysis than was the phosphate associated with the galacturonic acid. It is suggested that the more resistant phosphate is attached to either mannose or glucose, or to both.