Use of F-19 NMR as a direct probe of Delta(9) desaturase cryptoregiochemistry: A feasibility study

F-19 NMR can be used to monitor the relative efficiency with which various fluorinated aromatic sulfides are oxidized by the Delta 9 desaturating system of Saccharomyces cerevisiae. Thus the sulfoxy acids produce from methyl S-(4-(trifluoromethyl)benzyl)-8-mercaptooctanoate (3d), methyl S-(4-(trifluoromethyl)phenyl-2-ethyl))-8-mercaptooctanoate (3e), and methyl S-(4-(trifluoromethyl)benzyl)-9-mercaptononanoate (4c) were observed in the supernatant of S. cerevisiae cultures at concentrations of similar to 140, similar to 45, and similar to 10 mu M, respectively. This paper lays the methodological basis for a novel, in vitro ''thia test'' of cryptoregiochemistry and provides further experimental evidence that the yeast Delta 9 desaturase initiates oxidation of stearoyl CoA at C-9.