Location of functional groups in mycobacterial meromycolate chains; the recognition of new structural principles in mycolic acids

Abstract

Mycobacterial α-, methoxy-and keto-mycolic acid methyl esters were separated by argentation chromatography into mycolates with no double bond, with one trans double bond or with one cis double bond. Meromycolic acids were prepared from each methyl mycolate fraction by pyrolysis, followed by silver oxide oxidation, and analysed by high-energy collision-induced dissociation/fast atom bombardment MS to reveal the exact locations of the functional groups within the meromycolate chain. The locations of cis and trans double bonds, cis and trans cyclopropane rings, methoxy and keto groups, and methyl branches within the meromycolate chain were determined from their characteristic fragment ion profiles, and the structures of the meromycolic acids, including those with three functional groups extracted from Mycobacterium tuberculosis H37Ra, Mycobacterium bovis BCG and Mycobacterium microti, were established. Meromycolic acids with one cis double bond were structurally closely related to those with one cis cyclopropane ring, whereas the meromycolic acids with one trans cyclopropane ring were closely related to the corresponding meromycolic acids with one cis cyclopropane ring. A close relationship between methoxy-and keto-meromycolic acids was also implied. The relationship between the meromycolic acids with a trans double bond and the other meromycolic acids was not clearly revealed, and they did not appear to be immediate substrates for trans cyclopropanation.

The mmaA2 Gene of Mycobacterium tuberculosis Encodes the Distal Cyclopropane Synthase of the α-Mycolic Acid

“…This mass corresponds to a dicyclopropanated ␣-mycolate of 79 total carbons with a 24-carbon ␣ branch as pictured in Fig. 1 and as reported previously for other strains of Mtb (24,25). In addition, peaks at 1123 and 1179 reflect smaller and longer chain length variants by two methylene units.…”

Towards understanding the functional diversity of cell wall mycolic acids of Mycobacterium tuberculosis

“…Thus changes in the proportion of methoxy-and keto-MA had already been reported during cultivation of Mycobacterium microti [26]. In a second landmark paper, Watanabe et al identified and collated the positions of the functional groups in the meromycolate fragments of the MA, revealing the full complexity of the mixtures present and again showing considerable difference between H37Ra and other M.tuberculosis strains [25]. Table 2 lists the major components of the series of homologues identified for M.tuberculosis that contain two functionalities X and Y in the chain.…”

“…The detailed patterns of the mycolic acid components of a number of strains of M. tuberculosis and some other mycobacteria have been elegantly collected through the work of Watanabe et al [24,25]. The total mixture of methyl esters was analysed first by 1 H NMR spectroscopy, then separated into α-, methoxy and ketomycolates.…”

The use of biodiversity as source of new chemical entities against defined molecular targets for treatment of malaria, tuberculosis, and T-cell mediated diseases: a review

“…α-Mycolates: its meromycolate chain contains two ciscyclopropanes; Methoxymycolates: its meromycolate chain contains an a-methyl methyl-ether moiety in the distal position and a ciscyclopropane or an α-methyl trans-cyclopropane in the proximal position; Ketomycolates: its meromycolate chain contains an α-methyl ketone moiety in the distal position and proximal functionalities as in the methoxy series. It should be pointed out that, more recently, unsaturations have been detected in the meromycolate chain of M. tuberculosis (Watanabe et al 2002), which are not shown here. (Kremer et al 2003).…”