Branched-chain fatty acid biosynthesis in a branched-chain amino acid aminotransferase mutant of Staphylococcus carnosus

• Published in: FEMS microbiology letters Vol. 243; no. 1; pp. 37 - 44
• Main Author: Beck, Hans C.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Elsevier B.V 01.02.2005; Blackwell Publishing Ltd; Blackwell; Oxford University Press
• Subjects: Acid production; Amino acids; Bacteriology; Biological and medical sciences; Biosynthesis; Biotechnology - methods; branched chain amino acids; branched chain fatty acids; Branched-chain amino acid aminotransferase; Branched-chain fatty acid biosynthesis; Carboxylic acids; Cell Membrane; Cell membranes; Chain branching; Culture Media; Deuteration; Fatty acid composition; Fatty acids; Fatty Acids - biosynthesis; flavor compounds; Flavoring Agents; Fundamental and applied biological sciences. Psychology; Growth factors; Isobutyric acid; Isoleucine; Leucine; Metabolism. Enzymes; Metabolites; Microbiology; Mutants; Mutation; Secondary metabolites; Staphylococcus - enzymology; Staphylococcus - genetics; Staphylococcus - growth & development; Staphylococcus carnosus; Supplements; Transaminases - biosynthesis; Transaminases - genetics; Valine; Branched-chain fatty acid biosynthesis; Staphylococcus carnosus; Branched-chain amino acid aminotransferase; Enzyme; Metabolite; Transferases; Branched-chain-amino-acid transaminase; Lipids; Biosynthesis; Fatty acids; Growth curve; Branched chain; Transaminases; Bacteria; Micrococcales; Micrococcaceae; Mutation
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2004.11.041

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 α-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, α-keto-β-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-C 15:0, and from 3.6% to 33.9% iso-C 14:0 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.