Sources of lipoxygenase

In humans, the other route recognized for LX biosynthesis occurs between cell types of the vasculature. These intravascular sources of lipoxygenase products sharply contrast interstitial or mucosal origins. This pathway is best studied... 

Lipoxygenase products are produced by a variety of other inflammatory cells, organ parenchyma and vascular tissue " °L The effect of endotoxin or other noxious stimuli on these tissues and their potential importance as sources of lipoxygenase products in endotoxaemia and sepsis remain to be determined. 

Encompassing approx 6000 medicinal plant species, the medicinal flora of Asia and the Pacific comprise a fantastic source of pharmacologically active products, and the number of plant species principally used for the treatment of inflammation can be estimated to be more that 380. This chapter will focus on the potentials of medicinal plants of Asia as a source of original anti-inflammatory drugs, with particular interest payed to inhibitors of phospholipase A2, COX, lipoxygenases, elastase, and NOS. 

Hyperforin, the major constituent in Hypericum perforatum (St. John s Wort), inhibits the enzymatic activity of 5-lipoxygenase and COX-1 in platelets, acts as a dual inhibitor of 5-lipoxygenase and COX-1, and might have some potential in inflammatory and allergic diseases connected to eicosanoids (32), Several Hypericum species are of medicinal value in Asia and the Pacific. One of these is Hypericum erectum Thunb., the potential of which as a source of 5-lipoxygenase is given here. 

Soy beans are another crop that will not grow in Europe. The soy bean is used as a source of both protein and vegetable oil. Enzyme active soy flour has been used in bread since the 1930s. The flour contains a lipoxygenase system that assists with the development of the dough and slightly bleaches the bread. Soy flour is classed as an ingredient rather than an additive. 

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. 

When it became clear that the lipoxygenase pathway in mammalian systems was the source of previously unknown, but very important, biochemical transmitters. 

The X-ray crystal structure of mammalian 15-LOXl has revealed two domains, a catalytic domain and a j3-barrel domain [32], The P-barrel domain is similar to C2 domains found on other proteins and directs the binding of this enzyme to phospholipid membranes, the source of either AA or phospholipids for the oxidation process. The catalytic domain, which contains the histidine-coordinated Fe(III), holds the AA assisted by an ionic bond between R403 and the ionized carboxyl group of AA. The methyl terminus of AA is thus placed deep within a hydrophobic binding cleft in an arrangement that is likely similar to that of other lipoxygenases. 

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