PREPARATION OF C-13-LABELED POLYUNSATURATED FATTY-ACIDS BY AN ARACHIDONIC ACID-PRODUCING FUNGUS MORTIERELLA-ALPINA 1S-4

Three types of C-13-labeled polyunsaturated fatty acids (PUFAs) were p roduced in mycelia of an arachidonic acid-producing fungus, Mortierell a alpina 1S-4, when grown with C-13-labeled glucose or fatty acid meth yl esters. We analyzed them by negative-ion fast-atom bombardment mass spectrometry. (i) PUFA in mycelia grown with [1-C-13]glucose or [2-C- 13]glucose was a mixture of molecules containing zero to six labeled c arbons. The content of C-13 in the total carbon atoms of PUFA, such as arachidonic (20:4 omega 6), dihomo-gamma-linolenic (20:3 omega 6), ga mma-linolenic (18:3 omega 6), and linoleic (18:2 omega 6) acids, in th e mycelia grown with [1-C-13]glucose or [2-C-13]glucose was about 11 o r 15%, respectively. More than 80% of these PUFA had more than one C-1 3 atom, (ii) When the fungus was grown with [U-C-13]glucose, the conte nt of PUFA molecules, all carbons of which were C-13-labeled, was abou t 20%, The percentage of C-13 in PUFA from [U-C-13]glucose was 78-83%, over 98% of which had more than one C-13 atom. The C-13 atoms in the labeled fatty acids formed from C-13-labeled glucose were thought to b e distributed at random by a two carbon-unit. (iii) The C-13 atom of P UFA in mycelia grown with 1-C-13-labeled fatty acid methyl esters was highly localized. More than half of the 20:4 omega 6 molecules had onl y one C-13 atom at C-3, C-5, or C-7 when the fungus was grown with met hyl [1-C-13]stearate, methyl [1-C-13]palmitate, or methyl [1-C-13]myri state, respectively. (C) 1995 Academic Press, Inc.