Structural analyses of novel glycerophosphorylated α-cyclosophorohexadecaoses isolated from X. campestris pv. campestris

Abstract

Novel periplasmic anionic cyclic glucans produced by Xanthomonas campestris pv. campestris were isolated by trichloroacetic acid treatment and various chromatographic techniques. No report has been made on the presence of substituted cyclic glucans of the Xanthomonas species. We show, for the first time, that X. campestris pv. campestris produces the anionic cyclic glucans with phosphoglycerol residues, the presence of which can be predicted by analyzing the sequence database with the aid of the NCBI RefSeq database. To analyze the structure of isolated anionic cyclic glucans analyses, we used NMR spectroscopy, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOFMS) and electrospray–ionization mass spectrometry (ESIMS). The results suggest that the novel anionic forms of the cyclic glucans of X. campestris pv. campestris are glycerophosphorylated α-cyclosophorohexadecaose with one or two phosphoglycerol substituents at the C-6 positions of the glucose residues.