Occurrence of 2‐Amino‐2‐deoxy‐hexuronic Acids as Constituents of Vibrio parahaemolyticus K15 Antigen

Acidic capsular polysaccharide of Vibrio parahaemolyticus A55 (05: K15) was esterified with ethylene oxide and then reduced with sodium borohydride. Hydrolysis of the reduced material gave two hexosamines identical with mannosamine (2‐amino‐2‐deoxy‐mannose) and gulosamine (2‐amino‐2‐deoxy‐gulose) on paper and ion‐exchange chromatograms. This fact suggested that the K15 antigen contained mannosaminuronic acid (2‐amino‐2‐deoxy‐mannuronic acid) and gulosaminuronic acid (2‐amino‐2‐deoxy‐guluronic acid). Direct acid hydrolysis of the antigen gave two 2‐amino‐2‐deoxy‐hexuronic acids. These two were identified as mannosaminuronic and gulosaminouronic acids by paper chromatography and paper electrophoresis, being compared with synthesized standard samples. Titration of acid form of the polysaccharide indicated that about 91.5% of the polysaccharide was composed of the N ‐acetyl‐hexosaminuronic acids.