Characterization of lipoxygenase extracts from Penicillum sp.

Biomasses of Penicillium camemberti and P. roqueforti strains were grown and harvested after 10 d of incubation, a period that corresponded to the maximal dry weight of mycelium as well as to lipoxygenase (LOX) activity. Partially purified LOX extracts were obtained by ammonium sulfate precipitation of the crude enzymatic extracts that had been recovered from the biomasses. The partially purified LOX extracts exhibited a preferential specificity toward free fatty acids, including linoleic, linolenic, and arachidonic acids, rather than fatty acid acylglycerols, including mono-, di-, and trilinolein. The K _m and V _max values of LOX activity were investigated. Normal-phase high-performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry analyses showed that the LOX activity of the microbial extracts converted linoleic acid mainly into the corresponding 9- and 13-hydroperoxides (HPOD). However, the production of a significant proportion of 10-HPOD, ranging from 4 to 9% of the total HPOD, was also demonstrated. In addition, the enantiomeric ratios of the 9- and 13-HPOD produced were determined at both pH optima by chiral-phase HPLC. The results indicated that an almost racemic mixture had been obtained which can be related to either low enantioselectivity of LOX or the presence of isozymes showing complementary enantioselectivity.