Antioxidative function and substrate specificity of NAD(P)H-dependent alkenal/one oxidoreductase. A new role for leukotriene B4 12-hydroxydehydrogenase/15-oxoprostaglandin 13-reductase

Abstract

There are several known routes for the metabolic detoxication of α,β-unsaturated aldehydes and ketones, including conjugation to glutathione and reduction and oxidation of the aldehyde to an alcohol and a carboxylic acid, respectively. In this study, we describe a fourth class of detoxication that involves the reduction of the α,β-carbon = carbon double bond to a single bond. This reaction is catalyzed by NAD(P)H-dependent alkenal/one oxidoreductase (AO), an enzyme heretofore known as leukotriene B4 12-hydroxydehydrogenase, 15-oxoprostaglandin 13-reductase, and dithiolethione-inducible gene-1. AO is shown to effectively reduce cytotoxic lipid peroxidation products such as 4-hydroxy-2-nonenal (HNE) (kcat = 4.0 x 103 min-1; kcat/Km = 3.3 x 107 min-1 M-1) and acrolein (kcat = 2.2 x 102 min-1; kcat/Km = 1.5 x 106 min-1 M-1) and common industrial compounds such as ethyl vinyl ketone (kcat = 9.6 x 103 min -1; kcat/Km = 8.8 x 107 min -1 M-1) and 15-oxoprostaglandin El (k cat = 2.4 x 103 min-1; kcat/K m = 2.4 x 109 min-1 M-1). Furthermore, transfection of human embryonic kidney cells with a rat liver AO expression vector protected these cells from challenge with HNE. The concentration of HNE at which 50% of the cells were killed after 24 h increased from ∼15 μM in control cells to ∼70 μM in AO-transfected cells. Overexpression of AO also completely abolished protein alkylation by HNE at all concentrations tested (up to 30 μM). Thus, we describe a novel antioxidative activity of a previously characterized bioactive lipid-metabolizing enzyme that could prove to be therapeutically or prophylactically useful due to its high catalytic rate and inducibility.

Publication Title

Journal of Biological Chemistry

Link to Full Text

Share

COinS