Lipoxygenase characteristics

Ford-Hutchinson AW Arachidonate 15-lipoxygenase characteristics and potential biological significance. Eicosanoids 1991 4 65-74. 

Lipid peroxidation may proceed by both enzymatic and nonenzymatic pathways. Enzymatic peroxidation is catalyzed by enzymes such as lipoxygenases and cyclooxygenases (COXs) and is considered in Chapter 26. One of the most important questions in the study of the mechanisms of lipid peroxidation is the characteristic of an initiation stage. Obvious... 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Iron-containing superoxide dismutases are present in many species of bacteria (Hassan and Fridovitch, 1978). These nonheme iron proteins have a characteristic set of EPR lines split about g = 4.2 in the ferric state, arising from the middle Kramers doublet of a rhombic high-spin site. Ferrous iron superoxide dismutase forms an S = I complex with NO that resembles the lipoxygenase-NO adduct by EPR criteria (I. Fridovich, T. Kirby, and J. C. Salerno, (1978) unpublished observations). 

Ketoprofen is a propionic acid derivative that inhibits both COX (nonselectively) and lipoxygenase. Its pharmacokinetic characteristics are given in Table 36-1. Concurrent administration of probenecid elevates ketoprofen levels and prolongs its plasma half-life. 

In some cases the action of lipoxygenase leads to development of a characteristic aroma. Galliard et al. (1976) found that the main aroma compounds of cucumber, 2-trans hexenol and 2-trans, 6-cis-nonadienal, are produced by reaction of linolenic acid and lipoxygenase to form hydroperoxide... 

Smith and Lands have also shown that the lipoxygenase reaction is accompanied by reaction inactivation of the enzyme. The reaction rate is characteristic for each substrate and increases with the extent of unsaturation. They postulate that the enzyme has two sites—one for the substrate and one for the product hydroperoxide. They proposed a highly speculative mechanism in which the hydroperoxide combines with O2 to... 

The characteristic taste of edible mushrooms is mainly derived from the flavour chemicals 3-octanol and l-octen-3-ol. In order to fermentatively generate mushroom flavours it is possible to cultivate higher mushrooms in a submerged fermenter and propagate them by the formation of mycelia. In the fermentation broth, l-octen-3-ol is detectable after some time. In the mushroom this substance is formed by a lipoxygenase using unsaturated fatty acids as a substrate [21 ]. 

CIC Vitamin C (300 mg/100 g fmit), citric acid and malic acid are responsible for the clean acidic taste of the fresh fruit. A high enzyme activity of a lipoxygenase produces high amounts of (E)-2-hexenal, hexanal and (E)-2-hexenol, all fruity green notes, characteristic of green apples. The cut surfaces develop at prolonged standing 2-heptenal, 2,4-nonadienal and l-octen-3-one, responsible for stale, fatty odour. Methyl butyrate and ethyl butyrate impart the ripe, fruity, estery, fresh, juicy impression. 

In the Table 1 the main characteristics of free and immobilised at pH = 5, 6 microbial lipoxygenase are shown. 

The enzyme, soybean lipoxygenase-1 (SLO), offers an excellent system in which to illustrate the power of Eq. (10.20) in reproducing experimental data. Several characteristics of SLO are impossible to interpret through a Bell-like tunneling correction. The KIE on k at, k at = 81 + 5, is nearly temperature independent,... 

Torres-Penaranda, A.V. C.A. Reitmeier L.A. Wilson WR. Fehr J.M. Narvel. Sensory characteristics of soymilk and tofu made from lipoxygenase-free and normal soybeans./. Food Sci. 1998, 63, 1084-1087. 

Lipoxygenases (EC 1.13.11.12, linoleate oxygen oxidoreductase) are found in many plants with soybeans having the highest activity. The characteristics of these enzymes were reviewed recently (Robinson et al., 1995 Gardner, 2003). Fujimaki et al. (1965) showed that lipoxygenase was associated with hexanal production in soybeans. 

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