Volume 230, number 1,2, 101-104 FEB 05703 March 1988 Biosynthesis of very long chain monounsaturated fatty acids by subcellular fractions of developing seeds Denis J. Murphy and Kumar D. Mukherjee* zyxwvutsrqponmlkjihgfedcbaZYXWVU University of Durham, Department of Botany, Science Laboratories, South Road, Durham DHI 3LE. England and *Bundesanstalt fir Fettforschung, Institut fir Biochemie und Technologie, H.P. Kaufmann-Institut, Piusallee 68, D-4400 Miinster, FRG Received 23 December 1987; revised version received 27 January 1988 Subcellular fractions from developing seeds of mustard (Sinapis al/m), honesty (Lunaria annua) and nasturtium (Tropaeo- lum mojus) synthesize very long chain cis (n-9) monounsaturated fatty acids, e.g. gadoleic (20:1), erucic (22:l) and nervonic (24: 1) acid, from oleoyl-CoA and malonyl-CoA by condensation reactions. The particulate 2000 x g and 15 000 x g fractions exhibit considerably higher elongase activities compared to the microsomal or oil body fractions, whereas the soluble (150 000 x g supernatant) fraction is devoid of such activities. Very long chain monounsaturated fatty acid; Elongase; Gadoleic acid; Erucic acid; Nervonic acid; (Developing seed) 1. INTRODUCTION Very long chain monounsaturated fatty acids, such as gadoleic, (n - 9), cis-icosenoic (20: 1), erucic, (n - 9) cis-docosenoic (22: 1), and ner- vonic, (n - 9) cis-tetracosenoic acid (24: 1), are major constituents of certain seed oils. These fatty acids are of considerable interest as renewable raw materials for oleochemicals [l]. Knowledge of the enzymes involved in the biosynthesis of very long chain monounsaturated fatty acids and isolation of these enzymes are prerequisites for genetic manipulation of oilseed plants for efficient pro- duction of such fatty acids. In higher plants, the synthesis of very long chain saturated fatty acids has been shown to occur by the condensation of stearoyl-CoA with malonyl- CoA [2-51; these membrane-bound elongases have been solubilized and partially purified from leek (Gallium porrum L.) epidermal cell microsomes 1671. Correspondence address: K.D. Mukherjee, Bundesanstalt fiir Fettforschung, Institut fur Biochemie und Technologie, H.P. Kaufmann-Institut, Piusallee 68, D-4400 Milnster, FRG Little is known so far about the elongases in- volved in the formation of very long chain mo- nounsaturated fatty acids in plants. Developing seeds of Crambe abyssinica [8], Tropaeolum majus [9], and Sinapis alba [lo] have been shown to elongate oleic acid to 20 : 1 and 22 : 1, apparently by successive condensations of oleoyl-CoA with malonyl-CoA, as shown recently for subcellular fractions from developing Brassica juncea seeds Vll. We report here the biosynthesis of very long chain monounsaturated fatty acids by subcellular fractions from developing seeds of S. alba, T. ma- jus and Lunaria annua, which have been found to contain large proportions of such fatty acids in the storage triacylglycerols [ 12- 141. 2. MATERIALS AND METHODS Plants of mustard (S. alba, variety Albatros), honesty (L. an- nua, garden variety) and nasturtium (T. majus, garden variety) were grown outdoors, and the developing seeds, collected be- tween 4 and 6 weeks after flowering, were either used im- mediately or kept frozen at -70°C before use. [I-i4C]Oleoy1-CoA (18 : I-CoA) (1.85 GBq.mmol-i) and [2-i4C]malonyl-CoA (1.59 GBq.mmol-‘), both from NEN, Published by Elsevier Science Publishers B. V. (Biomedical Division) 00145793/88/$3.50 0 1988 Federation of European Biochemical Societies 101