SUMMARY PARAGRAPH for FAA3
In order for yeast to utilize fatty acids, either as an energy source (via beta-oxidation) or for essential processes such as phospholipid biosynthesis and protein myristoylation, the fatty acids must first be converted into activated intermediates, acyl-CoAs, through thioesterification of fatty acids with coenzyme A. When fatty acids are synthesized de novo, activation is part of the process of synthesis and is accomplished by the same fatty acid synthetase complex (Fas1p-Fas2p) that initiates and elongates the fatty acid chain. However, yeast cells can also utilize exogenous, imported fatty acids, an ability that becomes essential if the fatty acid synthetase complex is inactivated by mutation or specific inhibitors such as cerulenin. These exogenous fatty acids are activated by one of five characterized yeast acyl-CoA synthetases: Faa1p, Faa2p, Faa3p, Faa4p, or Fat1p (see 4 and 5 for review).
Purified Faa3p has been demonstrated to have acyl-CoA synthetase activity. The in vitro activity of Faa3p is significantly lower than that of Faa1p or Faa2p for medium or long chain fatty acids (C9:0-C18:0)(2). Unlike Faa1p or Faa2p, Faa3p demonstrates in vitro activity on very long chain fatty acids such as C22:0 and lignoceric acid (C24:0) (2); however, mutant analysis indicates that, under most conditions, Fat1p is the major acyl-CoA synthetase for very long chain fatty acids (6, 7).
Last updated: 2010-02-11