Characterization of the linoleic acid Δ9 hydratase catalyzing the first step of polyunsaturated fatty acid saturation metabolism in Lactobacillus plantarum AKU 1009a

Linoleic acid Delta 9 hydratase, which is involved in linoleic acid saturation metabolism of Lactobacillus plantarum AKU 1009a, was cloned, expressed as a his-tagged recombinant enzyme, purified with an affinity column, and characterized. The enzyme required FAD as a cofactor and its activity was enhanced by NADH. The maximal activities for the hydration of linoleic acid and for the dehydration of 10-hydroxy-cis-12-octadecenoic acid (HYA) were observed at 37 degrees C in buffer at pH 5.5 containing 0.5 M NaCl. Free C16 and C18 fatty acids with cis-9 double bonds and 10-hydroxy fatty acids served as substrates for the hydration and dehydration reactions, respectively. The apparent K-m value for linoleic acid was estimated to be 92 mu M, with a k(cat) of 2.6.10(-2) s(-1) and a Hill factor of 3.3. The apparent K-m value for HYA was estimated to be 98 mu M, with a k(cat) of 1.2.10(-3) s(-1). (C) 2014, The Society for Biotechnology, Japan. All rights reserved.