Sub-cellular localization of fatty acid elongase in developing seeds of Lunaria annua and Brassica napus
1993
Whitfield, H.V. | Murphy, D.J. | Hills, M.J.
Homogenates of developing seeds from Lunaria annua and Brassica napus were subjected to sucrose density gradient centrifugation in the presence of 5 mM EDTA. Fatty acid elongase which synthesizes gadoleic (20:1) and erucic (22:1) acids from oleic acid (18:1) was located in microsomal membranes with equilibrium densities of 1.07 and 1.12 in L. annua. In B. napus the majority of elongase activity was found in a membrane fraction with an equilibrium density of 1.10, although some elongase was also present in a very light fraction (1.04). In both cases, the lighter membranes contained only antimycin A-insensitive cytochrome c:NADH oxidoreductase as an endoplasmic reticulum marker whereas the heavier elongase fractions contained both the oxidoreductase and CDP-choline: DAG cholinephosphotransferase as markers. At lower concentrations of EDTA, most of the organelle and membrane marker enzymes were found together at a density of 1.18 due to aggregation of membranes, probably caused by the presence of high concentrations of endogenous divalent cations.
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