Lipoxygenases: From Isolation to Application

Abstract

The positive effect of lipoxygenase, added as an enzyme-active soy flour, during the production of white bread is well established. In addition to increasing the mixing tolerance and overall dough rheology, lipoxygenase is also an effective bleaching agent. It is known that these effects are mediated by enzyme-coupled cooxidation of gluten proteins and carotenoids. However, the mechanism whereby these effects are achieved is not yet fully understood. In order to gain a better understanding into the reactions governing the beneficial effects of lipoxygenases in bread dough, an in-depth knowledge of the lipoxygenase catalytic mechanism is required. Until now no single review combining the molecular enzymology of lipoxygenase enzymes and their application in the baking industry has been presented. This review, therefore, focuses on the extraction and molecular characterization of lipoxygenases in addition to the work done on the application of lipoxygenases in the baking industry.

The Chemistry of Protein Oxidation in Food

“…In honey, glucose oxidase generates H 2 O 2 as a major antibacterial factor (inhibin) . Lipoxygenase, e.g., from soy flour, may lead to bleaching of wheat flour and doughs by lipid peroxidation and carotenoid degradation . Together with ascorbic acid, both glucoseoxidase and lipoxygenase are applied technologically in flour treatment agents (Section 5.1) .…”

Plant Polyphenols as Antioxidant and Antibacterial Agents for Shelf‐Life Extension of Meat and Meat Products: Classification, Structures, Sources, and Action Mechanisms

“…Also, the stereoconfiguration of LOXs may be specified; letter R (rectus—the priorities decrease in a clockwise manner) or letter S (sinister—the priorities decrease in a counterclockwise manner) is used in the LOXs designation (for example, 12S‐LOX and 12R‐LOX). Based on the structural features of the proteins, plant LOXs are divided into type 1 and type 2 (Baysal and Demirdoven ; Hayward and others ). Based on the phylogenetic relatedness, mammalian LOXs were divided into 4 main subtypes: platelet‐type 12S‐LOX, 15S/12S‐LOX, epidermis‐type 12S‐LOX, and 5S‐LOX (Kühn and Thiele ).…”

“…They concluded that most LOXs consist of a single polypeptide chain folding into 2 domains: a smaller N‐terminal β‐barrel domain and a larger C‐terminal mostly α‐helix domain, which contains the substrate‐binding pocket and the redox‐active nonheme iron, essential for the catalyzed reaction. Protein X‐ray crystallography studies have shown that, for all LOXs, the catalytic nonheme iron is octahedrically coordinated by 5 amino acid residues from the polypeptide chain and a hydroxide ligand (Ivanov and others ; Hayward and others ). In the case of soybean LOX1 and coral 8R‐LOX, the amino acid residue ligands are three His, one Asn and the C‐terminal amino acid residue, Ile (Figure ).…”

“…Octaedrically coordination of nonheme iron in the active site of LOXs (adapted from Hayward and others ).…”

Die Chemie der Proteinoxidation in Lebensmitteln

“…B. aus Sojamehl, wird zur Bleichung von Weizenmehl und ‐teigen eingesetzt, was sich auf Lipidperoxidations‐ und Carotinoxidationsreaktionen zurückführen lässt . Zusammen mit Ascorbinsäure werden Glucose‐Oxidase und Lipoxygenase technologisch in Backmitteln eingesetzt (siehe Abschnitt 5.1) . Lactoperoxidase (LPO) begründet die immanente antimikrobielle Aktivität von Frischmilch.…”