Synthesis of mycocerosic acids from methylmalonyl coenzyme A by cell-free extracts of Mycobacterium tuberculosis var. bovis BCG

Multimethyl-branched acids extracted from the cells of Mycobacterium tuberculosis var. bovis BCG were identified by combined capillary gas-liquid chromatography and mass spectrometry. These mycocerosic acids consisted of the products expected from elongation of n-C₁₈ and n-C₂₀ primers with methylmalonyl-CoA. A soluble enzyme preparation from M. tuberculosis var. bovis BCG incorporated methylmalonyl-CoA into mycocerosic acids. This incorporation was partially dependent on the addition of arachidoyl-CoA and this primer affected product distribution, indicating elongation of the primer. Maximal incorporation of methylmalonyl-CoA required the presence of both NADPH and NADH together with ATP and Mg²⁺. Added CoA, FMN, acyl carrier protein, or bovine serum albumin had no effect on the activity in either the presence or absence of ATP and Mg²⁺. The pH optimum for mycocerosic acid synthesis was 6.2. Under these conditions, methylmalonyl-CoA was incorporated into very long acids which were identified as mycocerosic acids by radio gas-liquid chromatography.