A crude extract from Mycobacterium tuberculosis var. bovis Bacillus Calmette-Guerin was previously shown to incorporate methylmalonyl-CoA into mycocerosic acids, exemplified by 2,4,6,8-tetramethyloctacosanoic acid, and malonyl-CoA into n-fatty acids (Rainwater D.L., and Kolattukudy, P.E. (1983) J. Biol. Chem. 258, 2979-2985). The presence of several fatty acid synthases with differences in substrate preference and product chain length was detected in the crude extract of M. tuberculosis var. bovis. Among them was a mycocerosic acid synthase which was purified to homogeneity using anion-exchange chromatography, gel filtration, affinity chromatography, and hydroxyapatite chromatography. This fatty acid synthase elongated long-chain fatty acyl-CoA primers using methylmalonyl-CoA and NADPH to produce multimethyl-branched mycocerosic acids. The enzyme was specific for methylmalonyl-CoA and would not incorporate malonyl-CoA into fatty acids. It elongated n-C6 to n-C20 CoA esters to generate primarily the corresponding tetramethyl-branched mycocerosic acids. Exogenous [1-14C]acyl-CoA and trideuteromethylmalonyl-CoA were incorporated into the multimethyl-branched fatty acids. Dodecyl sulfate electrophoresis showed that the enzyme had a molecular weight of 238,000, whereas gel filtration showed a native molecular weight of 490,000, indicating that the enzyme is composed of two monomers of identical molecular weight. The enzyme contained an acyl carrier protein-like segment as indicated by incorporation of [1-14C]pantothenate into the 238-kDa protein and production of 1 mol of taurine/mol of the monomer upon hydrolysis of performic acid-oxidized enzyme. It is concluded that the mycocerosis acid synthase is a multifunctional enzyme similar to the well-characterized multifunctional fatty acid synthases except for the substrate specificity.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - Jan 1 1985|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology