The Biosynthesis of 1-octene-3-ol by a Multifunctional Fatty Acid Dioxygenase and Hydroperoxide Lyase in Agaricus bisporus

Abstract

The biosynthetic pathway from linoleic acid to 1-octen-3-ol in <i>Agaricus bisporus</i> has long been established, in which linoleic acid is converted to 10-hydroperoxide (10-HPOD) by deoxygenation, and 10-HPOD is subsequently cleaved to yield 1-octene-3-ol and 10-oxodecanoic acid. However, the corresponding enzymes have not been identified and cloned. In the present study, four putative genes involved in oxylipid biosynthesis, including one lipoxygenase gene named <i>AbLOX</i>, two linoleate diol synthase genes named <i>AbLDS</i>1 and <i>AbLDS</i>2, and one hydroperoxide lyase gene named <i>AbHPL</i> were retrieved from the <i>A. bisporus</i> genome by a homology search and cloned and expressed prokaryotically. <i>Ab</i>LOX, <i>Ab</i>LDS1, and <i>Ab</i>LDS2 all exhibited fatty acid dioxygenase activity, catalyzing the conversion of linoleic acid to generate hydroperoxide, and <i>Ab</i>HPL showed a cleaving hydroperoxide activity, as was determined by the KI-starch method. <i>Ab</i>LOX and <i>Ab</i>HPL catalyzed linoleic acid to 1-octen-3-ol with an optimum temperature of 35 °C and an optimum pH of 7.2, whereas <i>Ab</i>LDS1, <i>Ab</i>LDS2, and <i>Ab</i>HPL catalyzed linoleic acid without 1-octen-3-ol. Reduced <i>AbLOX</i> expression in antisense <i>AbLOX</i> transformants was correlated with a decrease in the yield of 1-octen-3-ol. <i>Ab</i>LOX and <i>Ab</i>HPL were highly homologous to the sesquiterpene synthase Cop4 of <i>Coprinus cinerea</i> and the yeast sterol C-22 desaturase, respectively. These results reveal that the enzymes for the oxidative cleavage of linoleic acid to synthesize 1-octen-3-ol in <i>A. bisporus</i> are the multifunctional fatty acid dioxygenase <i>Ab</i>LOX and hydroperoxide lyase <i>Ab</i>HPL.