Oxidation of C18 Hydroxy-Polyunsaturated Fatty Acids to Epoxide or Ketone by Catalase-Related Hemoproteins Activated with Iodosylbenzene

AbstractSmall catalase-related hemoproteins with a facility to react with fatty acid hydroperoxides were examined for their potential mono-oxygenase activity when activated using iodosylbenzene. The proteins tested were aFusarium graminearum 41  kD catalase hemoprotein (Fg-cat, gene FGSG_02217), aPseudomonas fluorescens Pfl01 catalase (37.5  kD, accession number WP_011333788.1), and aMycobacterium avium ssp.paratuberculosis 33  kD catalase (gene MAP-2744c). 13-Hydroxy-octadecenoic acids (which are normally unreactive) were selected as substrates because these enzymes react specifically with the corresponding 13S-hydroperoxides (Pakhomovaet al. 18:2559 –2568,5; Tederet al. 1862:706 –715,14). In the presence of iodosylbenzene Fg-cat converted 13S-hydroxy-fatty acids to two products: the 15,16-double bond of 13S-hydroxy α-linolenic acid was oxidized stereospecifically to the 15S,16R-cis-epoxide or the 13-hydroxyl was oxidized to the 13-ketone. Products were identified by UV, HPLC, LC –MS, NMR and by comparison with authentic standards prepared for this study. The Pfl01-cat displayed similar activity. MAP-2744c oxidized 13S-hydroxy-linoleic acid to the 13-ketone, and epoxidized the double bonds to form the 9,10-epoxy-13-hydroxy, 11,12-epoxy-13-hydroxy, and 9,10-epoxy-13-keto derivatives; equivalent transformations occurred with 9S-hydroxy-linoleic acid as substrate. In parallel incubations in the presence of iodosylbenzene, human catalase displayed no activity towards 1...

Source: Lipids - June 19, 2017 Category: Lipidology Source Type: research