The 6-O-Methylglucose-containing Lipopolysaccharide of Mycobacterium phlei

Abstract

The polysaccharide containing 6-0-methylglucose, from Mycobacterium phZei, is an acidic molecule with at least seven 6-U-methyl-n-glucopyranosyl residues linked (Y -1,4', and with a side chain of at least three a-l ,4'-n-glucopyranosyl units.A simplified procedure is described for isolating the polysaccharide (MGP) from acetone-dried M. Phlei cells with improved yield.Exhaustive cY-amylase digestion of the polysaccharide released glucose, maltose, and a disaccharide.The last yielded D-&COSe and 3-O-methyl-D-glucose after acid hydrolysis; while hydrolysis, after reduction with sodium borohydride, gave glucitol and 3-0-methylglucose.Methylation analysis established that the disaccharide was 3.O-methylcr-D-glucopyranosyl-( 1-4)-D-glucose.Limited a-amylolysis of MGP yielded a trisaccharide and a tetrasaccharide, each containing 1 mole of 3-O-methylglucose at the nonreducing end.The trisaccharide was digested by a-amylase to the disaccharide 3-O-methylglucosyl-(1 + 4).glucose and glucose, while cu-amylolysis of the tetrasaccharide gave these products plus maltose.A glucoamylase preparation converted the tetrasaccharide to the trisaccharide and glucose.That 3-0-methylglucose was at the nonreducing terminus of each saccharide was shown by partial acid hydrolysis studies and by the products of exhaustive propylation, which yielded 3-O-methyl-2,4,6-tri-Opropylglucose.Propylation of the intact polysaccharide and analysis of the fully alkylated methylglucosides by gas-liquid chromatography established that 3-0-methylglucose and glucose were in the nonreducing terminal positions.After a-amylase digestion, glucose was the only terminal residue.Glucoamylase removed an additional glucosyl residue, which had been linked (Y-1,4'to a 6-0-methylglucosyl residue.An organic acid having the chromatographic and electrophoretic properties of glyceric acid was isolated from acid * This work was supported by Grants AM884.AM8845, Ah110109, and TI-GM31 from the United States I'il6lic Heal& Service and