Oxidase carotene

The Chemistry and Biochemistry of Carotene Oxidases, Cell Regulation, and Cancer... 

In 1940 J. B. Sumner and R. J. Sumner (10) and Tauber (11) recognized that the fat oxidase or lipoxidase and carotene oxidase were identical. From their work it became clear that the enzyme catalyzed the peroxidation of unsaturated fats as the primary reaction and that carotene destruction occurred only during the active enzymatic attack on the fat in a coupled reaction. 

Considerable purification of lipoxygenase from soybeans was achieved by Balls et al (15), They used conventional protein purification methods and the carotene oxidase reaction to follow the enzyme activity. Theorell et al, (16), in 1947, crystallized the enzyme, or more correctly, one of the several isoenzymes in soybean. We believe this was lipoxygenase-1 as described later. 

Isoenzymes. Kies (90), who questioned the identity of lipoxygenase and carotene oxidase, thought that the lipoxygenase activity of soybeans was caused by more than one enzyme. She discovered that a partially... 

Other enzymes of this type have also been termed fat oxidase, carotene oxidase and lipoxidase (cf. Galliard and Chan, 1980). 

Enzymes of this type were formerly known as fat oxidase, carotene oxidase, and lipoxidase lipoxydase in French) and have also been listed under E.C. 1.99.2.1 and E.C. 1.13.1.13. It should be emphasized that several species of enzyme, distinguishable by substrate and product specificities as well as by physical properties, are covered by the generic term lipoxygenase. ... 

Indications that soybeans contained more than one form of LOX came from the apparent loss of carotene oxidase activity in partially purified LOX (Kies, 1947), from studies on the relative activities on triacylglycerol or free fatty acid substrates (Koch et al., 1958), and from the effects, of purification (Dolev et al., 1967) or pH (Galliard and Phillips, 1971) on the proportions of the 9- and 13-hydroperoxides formed. Guss et al. (1967, 1968a) found several electrophoretically distinguishable bands of LOX in soybean extracts. Characterization of different forms of LOX followed the isolation by Christopher et al. (1970) of an isoenzyme different from the Theorell type. 

The ability of LOX to catalyze cooxidation reactions has long been recognized (e.g., its carotene oxidase activity see Section I) and has been used as the basis for some LOX assays (see Section IV) and in commercial applications e.g., soybean or Vida faba flours (both rich in LOX activity) are added to bleach wheat flour pigments in white bread production. Cooxidation is clearly manifested in the bleaching of pigments (chlorophyll, carotenoids, etc.) but also results in the oxidation of protein-SH groups and of unsaturated fatty acids, including substrates for LOX. 

Lipoxygenases from different sources differ in their cooxidation activity. Enzymes from peas and beans (Phaseolus sp.) and the LOX-2 from soybean have a high cooxidation potential potato LOX is intermediate, whereas wheat, flax, and soybean LOX-1 have poor cooxidation activity (Grosch et al., 1976, 1977). Thus, the carotene oxidase activity of soybeans is associated with the LOX-2 isoenzyme, and this explains the observed selective loss of carotenoid bleaching activity during the purification and heat treatment of the classic (i.e., LOX-1) enzyme from soybean (Kies et al., 1969). 

The presence of a lipid-oxidizing enzyme in plants, then termed lipoxidase, was first described by Andre and Hou in 1932 [1]. A pigment bleaching property, attributed to a separate enzyme activity described as carotene oxidase, was later found to originate from this enzyme as well [2]. The name lipoxygenase (linoleateioxygen oxidoreductase, EC 1.13.11.12) is now used for this enzyme. 

The oxidation of carotenes results in the formation of a diverse array of xanthophylls (Fig. 13.7). Zeaxanthin is synthesised from P-carotene by the hydroxylation of C-3 and C-3 of the P-rings via the mono-hydroxylated intermediate P-cryptoxanthin, a process requiring molecular oxygen in a mixed-function oxidase reaction. The gene encoding P-carotene hydroxylase (crtZ) has been cloned from a number of non-photosynthetic prokaryotes (reviewed by Armstrong, 1994) and from Arabidopsis (Sun et al, 1996). Zeaxanthin is converted to violaxanthin by zeaxanthin epoxidase which epoxidises both P-rings of zeaxanthin at the 5,6 positions (Fig. 13.7). The... 

Hot water treatment was reported to delay carotenoid synthesis and thus yellowing of broccoli florets (at 40°C for 60 min) and kale (at 45°C for 30 min), but did not affect Brussels sprouts (Wang 2000). Hot air treatment (38°C and 95% RH for 24 hr) slightly decreased lycopene and (3-carotene content in tomato fruit (Yahia and others 2007) however, fruit heated at 34°C for 24 hr and stored 20°C developed higher lycopene and (3-carotene than nonheated fruit (Soto-Zamora and others 2005). Moist (100% RH) hot air (48.5 or 50°C) for 4 hr caused injury to papaya and losses in lycopene and (3-carotene, but similar treatment with dry air (50% RH), alone or in combination with thiabendazole, had no effect on lycopene and (3-carotene (Perez-Carrillo and Yahia 2004). High-temperature treatment also suppressed 1-aminocyclopropane-l-carboxylic acid oxidase activity and thus indirectly prevented carotenoid synthesis (Suzuki and others 2005). 

Figure 2.3. Oxidative cleavage of j6-carotene by carotene dioxygenase (EC 1.14.99.36), and onward metabolism of retinaldehyde catalyzed by retinol dehydrogenase (EC 1.1.1.105) and retinaldehyde oxidase (EC 1.2.3.11).

Trypanosomatids, as well as G. lamblia and Trichomonas spp. lack xanthine oxidase and therefore uric acid, another free radical scavenger, is absent. In contrast, a xanthine oxidase activity has been reported in Ancylostoma ceylanicum and Nippostrongylus brasiliensis (37). There are no reports of the presence of vitamin E and / -carotene in parasites. 

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