Self‐Inactivation by 13‐Hydroperoxylinoleic Acid and Lipohydroperoxidase Activity of the Reticulocyte Lipoxygenase

Abstract

1. The self-inactivation of lipoxygenase from rabbit reticulocytes with linoleic acid at 37 "C is caused by the product 13-hydroperoxylinoleic acid. This inactivation is promoted by either oxygen or linoleic acid.2. Lipohydroperoxidase activity was demonstrated with 13-hydroperoxylinoleic acid plus linoleic acid as hydrogen donor under anaerobic conditions at 2 "C. The products were 13-hydroxylinoleic acid, oxodienes and compounds of non-diene structure similar to those produced by soybean lipoxygenase-I .3. 13-Hydroperoxylinoleic acid also changed the absorbance and fluorescence properties of reticulocyte lipoxygenase. The results indicate that one equivalent of 13-hydroperoxylinoleic acid converts the enzyme from the ferrous state into the ferric state as described for soybean lipoxygenase-1. The spectral changes were reversed by sodium borohydride at 2 "C, but not at 37°C; it is assumed that the ferric form of reticulocyte lipoxygenase suffers inactivation.

Catalytic Multiplicity of 15-Lipoxygenase-1 Orthologs (ALOX15) of Different Species

“…A similar oxygen dependence of the LOX activation was recently reported for ALOXE3 [130]. Rabbit ALOX15 undergoes suicidal inactivation during the oxygenation of polyenoic fatty acids [39]. Initially, it has been suggested that the hydroperoxy fatty acids formed may oxidize catalytically relevant amino acids at the active site.…”

“…A lipohydroperoxidase activity has also been described for rabALOX15 [39,151]. As for humALOXE3 this catalytic activity was not restricted to anaerobic conditions, but also occurs when oxygen is present [152,153].…”

“…This enzyme oxidation occurs during the kinetic lag-phase. (2) At later stages of fatty acid oxygenation, rabALOX15 undergoes suicidal inactivation [39]. Unfortunately, the molecular basis for this enzyme inactivation still remains unclear.…”

“…They oxygenate polyenoic fatty acids to hydroperoxy derivatives but also exhibit a lipohydroperoxidase activity (sometimes also called hydroperoxide isomerase activity) [39,126,127] which converts lipid hydroperoxides to secondary lipid peroxidation products. The oxygenase activity involves hydrogen abstraction from a bisallylic methylene of the fatty acid substrate as rate limiting step (Fig.…”

The Stereochemistry of the Reactions of Lipoxygenases and Their Metabolites. Proposed Nomenclature of Lipoxygenases and Related Enzymes

“…However, for the activation only the occurrence of a hydroperoxy group is required, whereas the steric structure does not appear to be of importance. On the other hand, a high cellular level of hydroperoxy fatty acids may inactivate both lipoxygenase and cyclooxygenase (44,45). A steady state of hydroperoxide-generating and hydroperoxide-consuming processes seems to be important for the autoregulation of the lipoxygenase and cyclooxygenase pathways.…”