Mycolic acid

• Synthesis of the C26 saturated straight chain fatty acids by the enzyme fatty acid synthase-I (FAS-I) to provide the α-alkyl branch of the mycolic acids;
• Synthesis of the C56 fatty acids by FAS-II providing the meromycolate backbone;
• Introduction of functional groups to the meromycolate chain by numerous cyclopropane synthases;
• Condensation reaction catalysed by the polyketide synthase Pks13 between the α-branch and the meromycolate chain before a final reduction by the enzyme corynebacterineae mycolate reductase A (CmrA)^[6] to generate the mycolic acid; and
• Transfer of mycolic acids to arabinogalactan and other acceptors such as trehalose via the antigen 85 complex

The fatty acid synthase-I and fatty acid synthase-II pathways producing mycolic acids are linked by the

The mycolic acids show interesting inflammation controlling properties. A clear tolerogenic response was promoted by natural mycolic acids in experimental

The exact structure of mycolic acids appears to be closely linked to the virulence of the organism, as modification of the functional groups of the molecule can lead to an attenuation of growth in vivo. Further, individuals with mutations in genes responsible for mycolic acid synthesis exhibit altered cording.

Clinical relevance

An international multi-centre study has proved that

Mycolic acids with different sizes and chemical modifications are found throughout Mycobacteriales.[9]

Mycobacterium

Most attention have been traditionally devoted to the mycolic acids of Mycobacterium species, which display great variation in length and modifications. Modifications not seen in M. tuberculosis include:^[9]

• Double bonds (cis and trans), in M. smegmatis (with a branch from UmaA1) and M. alvei
• ω-1 methoxy, in M. alvei
• trans-epoxy group, in M. smegmatis
• Wax ester in S or cis position, in M. avium

Rhodococcus

The mycolic acids of members of the