title: Branched-chain fatty acid biosynthesis in a branched-chain amino acid aminotransferase mutant of Staphylococcus carnosus.
abstract: Fatty acid biosynthesis by a mutant strain of Staphylococcus carnosus deficient in branched-chain amino acid aminotransferase (IlvE) activity was analysed. This mutant was unable to produce the appropriate branched-chain alpha-ketoacid precursors for branched-chain fatty acid biosynthesis from the amino acids valine, isoleucine, and leucine, and required the short branched chain acids 2-methylbutanoic acid or 2-methylpropanoic acid for growth in a defined medium. The isoleucine related metabolites, alpha-keto-beta-methylvaleric acid and 2-methylbutanal also served as growth factors. Growth in rich medium and growth in defined medium supplemented with 2-methylpropanoic acid lead to extensive alteration of the fatty acid composition in the cell membrane. In rich medium, a change from 51.7% to 17.1% anteiso-C15:0, and from 3.6% to 33.9% iso-C14:0 fatty acids as compared to the wild-type strain was observed. Despite the deficiency in IlvE activity, the mutant strain was still able to produce the short chain carboxylic acids, 3-methylbutanoic acid and 2-methylpropanoic acid when cultivated in rich medium. Supplementation experiments employing deuterated glucose induced the valine biosynthetic pathway for 2-methylpropanoic acid production, revealing that the IlvE protein plays an important, but not essential role in the biosynthesis of branched-chain fatty acids and secondary metabolites in S. carnosus.
authors.affiliation: Danish Technological Institute, Holbergsvej 10, DK-6000 Kolding, Denmark. hans.christian.beck@teknologist.dk
authors.forename: Hans C
authors.initials: HC
authors.lastname: Beck
mesh_terms: D001709:Biotechnology / Q000379:methods; D002462:Cell Membrane; D003470:Culture Media; D005227:Fatty Acids / Q000096:biosynthesis*; D005421:Flavoring Agents; D009154:Mutation; D013210:Staphylococcus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D000637:Transaminases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D003470:Culture Media; D005227:Fatty Acids; D005421:Flavoring Agents; D000637:Transaminases; C019798:branched-chain-amino-acid transaminase