Characterization of a lipoxygenase extract from Geotrichum candidum

Geotrichum candidum was cultivated and harvested after 8 days of incubation, a period that corresponded to the maximal dry weight of mycelium as well as to optimal lipoxygenase (LOX) activity. A partially purified LOX enzymic extract was obtained by ammonium sulfate precipitation. The LOX extract exhibited two major activities, at pH 8.00 and 3.75 using linoleic acid as substrate. At pH 3.75, the enzymic extract displayed the highest specific activity using linolenic and linoleic acids as substrates whereas, at pH 8.00, maximal LOX activity was obtained using arachidonic and linoleic acids. At pH 3.75, fatty acid acylglycerols were enzymically oxidized with a similar efficiency to that obtained with free fatty acids. K-m and V-max values as well as the effect of a wide range of chemical substances on LOX activity were also investigated. High-performance liquid chromatography and gas chromatography/mass spectrometry analyses showed that LOX activity in the microbial enzymic extract converted linoleic acid to the corresponding 9- and 13-hydroperoxides. (C) 1999 Elsevier Science Ltd. All rights reserved.