Enzymic Oxidations

Oxidative Reactions. The majority of pesticides, or pesticide products, are susceptible to some form of attack by oxidative enzymes. For more persistent pesticides, oxidation is frequently the primary mode of metaboHsm, although there are important exceptions, eg, DDT. For less persistent pesticides, oxidation may play a relatively minor role, or be the first reaction ia a metaboHc pathway. Oxidation generally results ia degradation of the parent molecule. However, attack by certain oxidative enzymes (phenol oxidases) can result ia the condensation or polymerization of the parent molecules this phenomenon is referred to as oxidative coupling (16). Examples of some important oxidative reactions are ether cleavage, alkyl-hydroxylation, aryl-hydroxylation, AJ-dealkylation, and sulfoxidation. 

An important function of certain carotenoids is their provitamin A activity. Vitamin A may be considered as having the stmcture of half of the P-carotene molecule with a molecule of water added at the end position. In general, all carotenoids containing a single unsubstituted P carotene half have provitamin A activity, but only about half the activity of P carotene. Provitamin A compounds are converted to Vitamin A by an oxidative enzyme system present in the intestinal mucosa of animals and humans. This conversion apparendy does not occur in plants (see Vitamins, VITAMIN a). 

Hurst (19) discusses the similarity in action of the pyrethrins and of DDT as indicated by a dispersant action on the lipids of insect cuticle and internal tissue. He has developed an elaborate theory of contact insecticidal action but provides no experimental data. Hurst believes that the susceptibility to insecticides depends partially on the cuticular permeability, but more fundamentally on the effects on internal tissue receptors which control oxidative metabolism or oxidative enzyme systems. The access of pyrethrins to insects, for example, is facilitated by adsorption and storage in the lipophilic layers of the epicuticle. The epicuticle is to be regarded as a lipoprotein mosaic consisting of alternating patches of lipid and protein receptors which are sites of oxidase activity. Such a condition exists in both the hydrophilic type of cuticle found in larvae of Calliphora and Phormia and in the waxy cuticle of Tenebrio larvae. Hurst explains pyrethrinization as a preliminary narcosis or knockdown phase in which oxidase action is blocked by adsorption of the insecticide on the lipoprotein tissue components, followed by death when further dispersant action of the insecticide results in an irreversible increase in the phenoloxidase activity as a result of the displacement of protective lipids. This increase in phenoloxidase activity is accompanied by the accumulation of toxic quinoid metabolites in the blood and tissues—for example, O-quinones which would block substrate access to normal enzyme systems. The varying degrees of susceptibility shown by different insect species to an insecticide may be explainable not only in terms of differences in cuticle make-up but also as internal factors associated with the stability of oxidase systems. 

Central core disease (CCD) is an autosomal dominant, non-progressive myopathy characterized by hypotonia and proximal muscle weakness in infancy. CCD is named after detection of characteristic central cores that lack both mitochondria and oxidative enzyme... 

Sumegi, B., Porpaczy, Z., Alkonyi, 1. (1991). Kinetic advantage of the interaction between the fatty acid P-oxidation enzymes and the complexes of the respiratory chain. Biochim. Biophys. Acta 1081, 121-128. 

Uchicda, Y., Izai, K., Orii, T., Hashimoto, T. (1992). Novel fatty acid p-oxidation enzymes in rat liver mitochondria. II. Purification and properties of enoyl-coenzyme A (CoA) hydratase/3-hy-droxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase trifunctional protein. J. Biol. Chem. 267, 1034-1041. 

Figure 3. Central core disease muscle fibers chondrial oxidative enzyme activity.

An important advance on these studies was the possibility of isolating AORs from Fe enriched media with obvious interest for an iron-sulfur center site labeling, with enhanced sensitivity of the Mossbauer studies. The work developed with bacterial systems is advantageous as compared with mammalian systems for isotopic labeling and opens the possibility of a direct measurement of substrate binding. Spectra of the enzyme in oxidized, partially reduced, benzaldehyde-reacted, and fully reduced states were recorded at different temperatures and with variable externally applied magnetic fields (222). In the oxidized enzyme, the clusters are diamag-... 

Oxygen lade Loss of blood supply, depletion of the oxygen-carrying capacity ofthe blood, poisoning of the oxidative enzymes. 

Parekh VR, RW Traxler, JM Sobek (1977) -alkane oxidation enzymes of a pseudomonad. Appl Environ Microbiol 33 881-884. 

Schneider S, G Fuchs (1998) Phenylacetyl-CoA acceptor oxidoreductase, a new a-oxidizing enzyme that produces phenylglyoxylate. Assay, membrane localization, and differential production in Thauera aro-matica. Arch Microbiol 169 509-516. 

Punnonen, K., Jansen, C.T., Puntala, A. and Ahotupa. M. (1991b). Effects of in vitro UVA irradiation and PUVA treatment on membrane fatty acids and activities of anti-oxidant enzymes in human keratinocytes. J. Invest. Dermatol. 96, 255-259. 

M (32% increase in liver weights 178% increase in peroxisomal beta-oxidation enzyme activity)... 

Duran, N. and Esposito, E., Potential applications of oxidative enzymes and phenoloxidase-like compounds in wastewater and soil treatment a review, Appl. Catal. B Environmental, 28, 83-99, 2000. 

Torres, E., Bustos-Jaimes, I., and Le Borgne, S., Potential use of oxidative enzymes for the detoxification of organic pollutants, Appl. Catal. B Environmental, 46, 1-15, 2003. 

Kay, K. (1970) Pesticides and associated health factors in agricultural environments effects on mixed-function oxiding enzyme metabolism, pulmonary surfactant and immunological reactions, in Pesticides Symposia, R. Dichmann (Ed.), Halos Co., Miami, FL. 

Hepatic 0.0015 0.005 (decreased glycogen, RNA, sulfhydryl groups, alterations in activities of oxidizing enzymes) ... 

Taking into account that heat treatment inactivates some oxidative enzymes and causes the rupture of some cellular structures, greater extractability of carotenoids is expected to occur in processed foods. Therefore, when mild temperatures are applied, it is very common to obtain higher carotenoid content in a processed food as compared to its fresh counter part. For example, total... 

In the experiment involving oxidative enzyme HRP (EC 1.11.1.7, RZ 1.9, 240 purpuro gallin (units/mg)) [89] for the enzymatic treatment and ultrasonic waves of 423 kHz and 5.5 W, the phenol degradation rate was found to increase. The ultrasound assisted biodegradation method has been found to be more efficient method than the sonolysis and enzyme treatment when operated individually. 

Entezari MH, Petrier C (2003) A combination of ultrasound and oxidative enzyme sono-biodegradation of substituted phenols. Ultrason Sonochem 10 241-246... 

Oxidative-pericydic processes, and in particular the oxidative/Diels-Alder reaction, are quite common in nature. The so-called Diels-Alderase is usually an oxidizing enzyme, which induces, for example, the formation of a suitable dienophile such as an enone from an allylic alcohol [49]. 

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