Molecular characterization of Lactobacillus plantarum genes for beta-ketoacyl-acyl carrier protein synthase III (fabH) and acetyl coenzyme A carboxylase (accBCDA), which are essential for fatty acid biosynthesis

Genes for subunits of acetyl coenzyme A carboxylase (ACC), which is the enz yme that catalyzes the first step in the synthesis of fatty acids in Lactob acillus plantarum L137, were cloned and characterized. We identified six po tential open reading frames, namely, manB, fabH, accB, accC, accD, and accA , in that order. Nucleotide sequence analysis suggested that fabH encoded b eta -ketoacyl-acyl carrier protein synthase III, that the accB, accC, accD, and accA genes encoded biotin carboxyl carrier protein, biotin carboxylase , and the beta and alpha subunits of carboxyltransferase, respectively, and that these genes were clustered. The organization of acc genes was differe nt from that reported for Escherichia coli, for Bacillus subtilis, and for Pseudomonas aeruginosa. E. coli accB and accD mutations were complemented b y the L. plantarum accB and accD genes, respectively. The predicted product s of all five genes were confirmed by using the T7 expression system in E. coli. The gene product of accB was biotinylated in E. coli. Northern and pr imer extension analyses demonstrated that the five genes in L. plantarum we re regulated polycistronically in an acc operon.