LOXPsa1, the first recombinant lipoxygenase from a basidiomycete fungus

A dioxygenase from the edible basidiomycete Pleurotus sapidus, originally researched because of its distinct ability to convert the sequiterpene (+)-valencene to the valuable grapefruit aroma (+)-nootkatone, was identified as a potent lipoxygenase (LOX(Psa)1). Kinetic parameters, pH and temperature optima of the pure recombinant enzyme were determined using linoleic acid as the substrate. K-m, v(max), and k(cat) were 40.3 mu M, 130.3 U mg(-1), and 157 s(-1), respectively. The maximal enzymatic activity was found at pH 7.0 and 35 degrees C. Showing high specificity toward free linoleic acid, the enzyme was classified as lipoxygenase type 1. Conversion of linoleic acid yielded mainly (S)-13-hydroperoxy-9Z,11E-octadecadienoic acid (94% ee), as was confirmed by chiral HPLC analysis of the hydroperoxides. The amino acid sequence showed homology to lipoxygenases catalyzing S stereospecific oxygenation, and thus the enzyme was characterized as a 13S-lipoxygenase. This is the first lipoxygenase described to accept terpene hydrocarbons as substrates. (C) 2012 Elsevier B.V. All rights reserved.