Abstract
The dipyruvylated glycolipid from Mycobacterium smegmatis (Saadat, S., and Ballou, C.E. (1983) J. Biol. Chem. 258, 1813-1818) has been shown to have the following structure in which FA1 is tetra- or hexadecanoic acid and FA2 is 2,4-dimethyl-2-eicosenoic acid. (formula; see text) The fast atom bombardment mass spectrum showed two major ions [M - H]- at m/z 1511 and 1539 (Mr 1512 and 1540) in a ratio of 1.4:1, suggesting that the glycolipid was a mixture of homologs that differed in fatty acid composition by 2 methylene groups. Analysis revealed C14, C16, and C22 fatty acids in ratios of 0.6:0.4:1.0, indicating that 60% of the molecules contained a C14 and C22 fatty acid whereas 40% contained a C16 and C22 fatty acid. The fragmentation pattern showed that a single glucose unit along with the smaller fatty acid could be lost to yield a tetrasaccharide with attached C22 fatty acid, and a second fragmentation yielded a trisaccharide containing 2 pyruvic acids but without attached fatty acid. The C14 and C16 fatty acids were identified as myristic and palmitic acid, whereas the C22 fatty acid was 2,4-dimethyl-2-eicosenoic acid. Precise localization of the fatty acids came from periodate oxidation and methylation analysis.
Highlights
The dipyruvylated glycolipid from Mycobacterium Hunter et al (3) subsequently noted the presence of a trehasmegmatis(Saadat,S., andBallou,C
FA1 the trehalose unit whereas the docosenoic acid isesterified to the other glucose of the trehalose unit
Distinguished by the presence of a trehalose unit as partof a Periodate oxidation was followed by the Avigad procedure (7) and pentasaccharide that contained a single 3-0-methylglucose and 2 pyruvate ketal units (1).It was noted that the glycolipid wasesterified by a mixtureof long-chain fatty acids with 14 to 22 carbon atoms
Summary
From the $Department of Biochemistry, University of California, Berkeley, California 94720 and the llDepartment of Biochemistry,Imperial College, London SW7,England. Methods-Gas chromatography of fatty acid methyl esters and yielded a trisaccharide containing 2 pyruvic acbidust sugar alditol acetates was done on a Varian 1400chromatograph with without attachedfatty acid. Distinguished by the presence of a trehalose unit as partof a Periodate oxidation was followed by the Avigad procedure (7) and pentasaccharide that contained a single 3-0-methylglucose and 2 pyruvate ketal units (1).It was noted that the glycolipid wasesterified by a mixtureof long-chain fatty acids with 14 to 22 carbon atoms. Earlier Brennan et al (2) had reported the presence of a mycobacterial glycopeptidolipid that containsa pyruvylated 3-0-methylglucose unit,and the formation of formic acid by an enzyme assay (8).The glycolipid (3.89 pmol) was oxidizedin 10 mM NaIO, in 0.2 M ammonium acetate at pH4 for 66 h. A hydroxamate assay was used t o determine the degree of esterification of the glycolipid (15)
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