Structure of a hydroxymycolic acid potentially involved in the synthesis of oxygenated mycolic acids of the <em>Mycobacterium tuberculosis</em> complex.

Mycolic acids are believed to play a crucial role in the architecture of the mycobacterial envelope. However, very few steps of their biosynthetic pathway have yet been elucidated. We previously isolated [Dubnau, E., Lanéelle, M. A., Soares, S., Bénichou A., Vaz, T., Promé, D., Promé, J. C. Daffé, M. & Quémard, A. (1997) Mycobacteriurn bovis BCG genes involved in the biosynthesis of cyclopropyl keto- and hydroxy-mycolic acids, Mol. Microbiol. 23, 313-322] a gene cluster from Mycobacteriun bovis BCG, cmaA-D, which confers upon M, smegmatis the ability to synthesize cyclopiopanated ketomycolic icid and a new type of mycolic acid which is hydroxylated. A meticulous analysis of all the mycoliclike fatty acids of M. bovis BCG and M. tuberculosis showed that these organisms produce small amounts of the hydroxymycolic acid. The structure of this molecule, determined by NMR spectroscopy, mass spectrometry and stereochemical studies, strongly suggests that there is a direct biosynthetic relationship between the keto- and the hydroxy-mycolic acids. [ABSTRACT FROM AUTHOR]