Structural relations between unsaturated mycolic acids and short-chain unsaturated acids synthesized by Mycobacterium phlei. Metabolic implications

Abstract

Mycobacterium phlei synthesizes a complex mixture of saturated and unsaturated fatty acids, with a normal or a branched chain. We have isolated the unsaturated fatty acids R–CH = CH–(CH2)n–CO2H, with twenty to twenty seven carbon atoms. These acids only make up a very small amount of the total fatty acids. Their structures were established by means of the oxidation method of Lemieux, followed by gas chromatographic analysis of the lower acids thus obtained.Some of these unsaturated acids (4‐eicosenoic, 6‐docosenoic, 8‐hexacosenoic acids) are likely to be metabolically related, whereas 5‐enoic fatty acids (normal chain 5‐enoic acids with 22, 24 or 26 carbon atoms and branched chain 5‐enoic acids with 25 and 27 carbon atoms) could arise through a common peculiar process.Simultaneously, by use‐of the same oxidation method, we have identified the radical R in the mycolic acids R–CH = CH–X–CH(OH)–CH(R')–CO2H. These radicals R are identical to the radicals R of the five different 5‐enoïc fatty acids. This observation suggests the hypothesis that these unsaturated acids play a role in the synthesis of the mycolic acids in Mycobacterium phlei. By a critical analysis of previous work in this field, we show that this hypothesis is consistent with all the results found in the literature.