Open AccessBranched‐chain fatty acid biosynthesis in a branched‐chain amino acid aminotransferase mutant of Staphylococcus carnosus
Author(s) -
Beck Hans C.
Publication year - 2005
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2004.11.041
Subject(s) - valine , isoleucine , biochemistry , biosynthesis , amino acid , fatty acid , leucine , mutant , branched chain amino acid , chemistry , biology , enzyme , gene
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 .