STRUCTURAL ELUCIDATION OF NOVEL METHYLGLUCOSE-CONTAINING POLYSACCHARIDES FROM MYCOBACTERIUM-XENOPI

The structures of methylglucose-containing polysaccharides (MeGlc PS) from Mycobacterium xenopi were investigated using high-pH anion-exchan ge chromatography end liquid secondary-ion mass spectrometry. We repor t the structure of two novel MeGlc PS, referred to as A and B. MeGlc P S A is composed of 16 D-glucopyranose residues, 11 of which are methyl ated, and MeGlc PS B contains 15 D-glucopyranose residues, 10 of which are methylated. The main structural feature of both MeGlc PS A and BI compared to the previously described structures, is the absence of th e tetrasaccharide non-reducing end 3-O-Me-D-Glcp-[alpha(1-->4)-D-Glcp] (3). The MeGlc PS A structure is similar to the synthetic polysacchari de [Saier, M. H. & Ballou, C. E. (1968) J. Biol. Chem. 243,992-1005], having a lower affinity for fatty acids than the MeGlc PS of Mycobater ium smegmatis [Kiho, T. & Ballou, C. E. (1988) Biochemistry 27, 5824-5 828]. Thus, the occurrence of MeGlc PS A and the consequences on the r egulation of fatty acid synthetase I activity involved in the biosynth esis of fatty acids, precursors of mycolic acid biosynthesis, is discu ssed.