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Structure and antigenicity of the major specific glycolipid antigen of Mycobacterium leprae
Abstract:
Earlier we reported on the presence of a specific phenolic glycolipid (Phenolic Glycolipid-I) in Mycobacterium leprae, and in infected armadillo tissues (Hunter, S. W., and Brennan, P. J. (1981) J. Bacteriol. 147, 728-735). It had an inherent oligosaccharide, composed of 3-O-Me-rhamnose, 2,3-di-O-Me-rhamnose, and 3,6-di-O-Me-glucose, glycosidically linked to the phenol substituent. The structure of the oligosaccharide has now been determined, by partial acid hydrolysis, permethylation, 1H NMR, and 13C NMR as: 3,6-di-O-Me-Glcp(1 beta leads to 4)2,3-di-O-Me-Rhap(1 alpha leads to 2)3-O-Me-Rhap1 alpha leads to phenol (assuming that the glucose substituent is in the D-enantiomeric configuration, and the two methylated rhamnoses are L). Acid hydrolysis of deacylated Phenolic glycolipid-I yielded a phenolic phthiocerol "core," and mass spectrometry and proton NMR of the permethylated core suggested the following structure: (formula, see text) Combined gas-liquid chromatography-mass spectrometry showed three tetramethyl branched "mycocerosic" acids, C30, C32 and C34, with molecular weights (as methyl esters) of 466, 494, and 522, respectively. These are esterified to the hydroxyl functions of the branched glycolic chain. Evidence is also presented that the glycolipid is immunologically active, reacting with rabbit antisera to M. leprae and with sera from lepromatous leprosy patients.
Insights
Researchers elucidated the structure of a phenolic glycolipid from Mycobacterium leprae. This lipid is immunologically active and found in leprosy patients, offering insights into disease mechanisms.
Area of Science:
- Microbiology
- Immunology
- Organic Chemistry
Background:
- Phenolic Glycolipid-I (PGL-I) was previously identified in Mycobacterium leprae and infected tissues.
- PGL-I contains an oligosaccharide linked to a phenol substituent.
Purpose of the Study:
- To determine the complete structure of the oligosaccharide component of PGL-I.
- To elucidate the structure of the phenolic phthiocerol core.
- To identify the mycocerosic acids esterified to the glycolipid.
Main Methods:
- Partial acid hydrolysis
- Permethylation analysis
- Proton (1H) and Carbon-13 (13C) Nuclear Magnetic Resonance (NMR) spectroscopy
- Gas-liquid chromatography-mass spectrometry (GLC-MS)
Main Results:
- The oligosaccharide structure was determined as 3,6-di-O-Me-Glcp(1β→4)2,3-di-O-Me-Rhap(1α→2)3-O-Me-Rhap1α→phenol.
- The phenolic phthiocerol core structure was proposed based on mass spectrometry and NMR.
- Three tetramethyl-branched mycocerosic acids (C30, C32, C34) were identified as esterified components.
Conclusions:
- The complete structure of Phenolic Glycolipid-I from Mycobacterium leprae has been elucidated.
- The glycolipid demonstrates immunological activity, reacting with antisera to M. leprae and sera from leprosy patients.