Mycobactins
Title: Mycobactins
Literature References: Growth factors for Mycobacterium paratuberculosis (M. johnei), the organism responsible for Johne's disease in cattle. Mycobactins are structurally complex siderophores (microbial iron chelators). At least nine mycobactins, designated with the letters A, F, H, M, N, P, R, S, and T, have been isolated from various non-pathogenic species of Mycobacterium. Earlier studies were actually on mycobactin P; see isoln from M. phlei: Francis et al., Nature 163, 365 (1949); eidem, Biochem. J. 55, 596 (1953); structure: Snow, ibid. 94, 160 (1965). Separation and identification of mycobactins: White, Snow, ibid. 108, 593 (1968); 111, 785 (1969). Chemical and biological properties: eidem, ibid. 115, 1031 (1969). On saponification, mycobactin splits into mycobactic acid and cobactin. Synthetic studies: Black et al., Aust. J. Chem. 25, 2155 (1972). Synthesis of mycobactin S2: P. J. Maurer, M. J. Miller, J. Am. Chem. Soc. 105, 240 (1983). Review of early studies: Rose, Snow, "Mycobactin: A Growth Factor for Acid-Fast Bacilli" in G. E. W. Wolstenholme, M. P. Cameron, C. M. O'Connor, Ciba Found. Symp. Exp. Tuberc. Bacillus Host 1955, 41-54. Comprehensive review: Snow, Bacteriol. Rev. 34, 99 (1970).
Properties: Able to chelate with metals, showing strong selectivity toward iron. Isolated as octahedral ferric complexes in the form of red-brown glasses; purified to metal-free mycobactins as white microcrystalline powders. Characterizations, esp mass spectral studies, carried out on the aluminum complexes. Mycobactin solids have definite melting points, are stable to air and heat up to about 100°, and show apple-green fluorescence in uv light. Characteristic uv max (methanol): 250, 311 nm for mycobactins having a methyl substituent on the benzene ring; 243, 249, 304 nm for mycobactins without the methyl substituent. Very sol in chloroform; fairly sol in ethanol; less sol in other alcoholic solvents. Slightly sol in benzene, ether, aliphatic hydrocarbons. Stable to acids; easily broken down under alk. conditions.
Absorption maximum: uv max (methanol): 250, 311 nm for mycobactins having a methyl substituent on the benzene ring; 243, 249, 304 nm for mycobactins without the methyl substituent
Use: In the taxonomy of mycobacteria; in development of iron chelators for clinical use.

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