Oxidase Reaction

The existence of chaotic oscillations has been documented in a variety of chemical systems. Some of tire earliest observations of chemical chaos have been on biochemical systems like tire peroxidase-oxidase reaction [12] and on tire well known Belousov-Zhabotinskii (BZ) [13] reaction. The BZ reaction is tire Ce-ion-catalyzed oxidation of citric or malonic acid by bromate ion. Early investigations of the BZ reaction used tire teclmiques of dynamical systems tlieory outlined above to document tire existence of chaos in tliis reaction. Apparent chaos in tire BZ reaction was found by Hudson et a] [14] aiid tire data were analysed by Tomita and Tsuda [15] using a return-map metliod. Chaos was confinned in tire BZ reaction carried out in a CSTR by Roux et a] [16, E7] and by Hudson and... 

Fig. 36 Dependence of the area of the chromatogram zone at constant amount of applied substance (1 pg) on the reagent employed, top relief representation, below zone areas projected on one another Iodine vapor reacts least sensitively here, aniline-phthalate most sensitively and the GOD reaction (glucose oxidase reaction) most specifically [2161...

Superoxide is formed (reaction 1) in the red blood cell by the auto-oxidation of hemoglobin to methemo-globin (approximately 3% of hemoglobin in human red blood cells has been calculated to auto-oxidize per day) in other tissues, it is formed by the action of enzymes such as cytochrome P450 reductase and xanthine oxidase. When stimulated by contact with bacteria, neutrophils exhibit a respiratory burst (see below) and produce superoxide in a reaction catalyzed by NADPH oxidase (reaction 2). Superoxide spontaneously dismu-tates to form H2O2 and O2 however, the rate of this same reaction is speeded up tremendously by the action of the enzyme superoxide dismutase (reaction 3). Hydrogen peroxide is subject to a number of fates. The enzyme catalase, present in many types of cells, converts... 

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... 

Approximately 10-20% of -hexane absorbed by inhalation is excreted unchanged in exhaled air the remainder is metabolized. Metabolism takes place via mixed-function oxidase reactions in the liver. In a study in which metabolites were measured in workers exposed to 77-hexane (Perbellini et al. 1981), mean concentrations of 77-hexane metabolites in urine were 2,5-hexanedione, 5.4 mg/L 2,5-dimethylfuran,... 

Spin-trapping experiments connected with biological superoxide production have also been used to examine the biochemistry of anti-tumour antibiotics bleomycin (Sugiura and Kikuchi, 1978) and mitomycin C (Lown et al., 1978), as well as the effect of iron concentration on xanthine oxidase reactions (Buettner et al., 1978), and the photochemistry of melanins (Felix et al., 1978). 

Hildebrandt A., Estabrook RW. 1971. Evidence for the participation of cytochrome b5 in hepatic microsomal mixed-function oxidase reactions. Arch Biochem Biophys 143 66-79. 

Kohen, A., Jonsson, T. and Klinman, J.P. (1997). Effects of protein glycosylation on catalysis changes in hydrogen tunnehng and enthalpy of activation in the glucose oxidase reaction. Biochemistry 36, 2603-2611... 

Brandange S, Lindblom L (1979) The enzyme aldehyde oxidase is animinium oxidase. Reaction with nicotine delta 1(5 ) iminium ion. Biochem Biophys Res Commun 91 991-996 Byrd GD, Chang KM, Greene JM, deBethizy JD (1992) Evidence for urinary excretion of glu-curonide conjugates of nicotine, cotinine, and trans-3 -hydroxycotinine in smokers. Drug Metab Dispos 20 192-197... 

Figure 7.40 The cytochrome c oxidase reaction cycle starting from the mixed-valence state.

The peroxidase-catalyzed transformations are classified as (1) the peroxidase reaction (Table 2, entries 1 -4), (2) the peroxygenase reaction (Table 2, entries 4-6) [25], and (3) the oxidase reaction (Table 2,entries 7-9). 

Figure 8.6 The three dehydrogenase (oxidase) reactions in amino acid degradation. The enzymes are D-amino acid oxidase, glutamate dehydrogenase and proline oxidase (dehydrogenase). Biochemical details are given in Appendix 8.4.

The oxidase reaction was first studied some years ago for the P. aeruginosa enz5une, but the most recent study, made in the knowledge of the crystal structure, has been on the enzyme from P. pantotrophus. In addition to providing some intriguing insights as to the oxidase reaction, this study has also provided valuable new information about the general properties of cytochrome cd. ... 

Although the matter cannot be regarded as completely settled, it seems likely that during the oxidase reaction a His/Met ferric c heme occurs. This might be expected to be more readily reduced by ascorbate than the His/His form, thus explaining the more rapid reduction of the enzyme by ascorbate after an initial oxidation by oxygen. Support for this view comes from the finding that the semi-apo enzyme is much more rapidly reduced by ascorbate than the as prepared oxidized holoenzyme. 

Scheme 2 Simplified catalytic cycle for palladium-catalyzed aerobic oxidation ( oxidase ) reactions...

Biosensors are also available for glucose, lactate, alcohol, sucrose, galactose, uric acid, alpha amylase, choline, and L-lysine. All are amperometric sensors based on O2 consumption or H2O2 production in conjunction with the turnover of an enzyme in the presence of substrate. In the case of glucose oxidase reaction, the normal biological reaction is ... 

Nagano, T., and Fridovich, 1. (1985). The co-oxidation of ammonia to nitrite during the aerobic xanthine oxidase reaction. Arch. Bixhem. Biophys. 241, 596-601. 

The enzymatic activity versus pH is thus generally a bell-shaped curve as in Fig. 6. An autocatalytic effect may appear when the reaction products have an acid-base effect (often the case). A simple example is the glucose oxidase reaction, shown in Fig. 7. Notably, the rate versus product (H+) curve indicates an autocatalytic effect on the alkaline branch, that is, for pH>pH (see Fig. 6). Systems presenting analogous properties have been studied by R. Caplan et al.27 and we also learn more about them from D. Thomas in this volume. 

In the case of an oxidase reaction, oxygen serves as an hydrogen acceptor and is reduced to either H20 [Eq. (3)] or H202 [Eq. (4)], where SH2 represents substrate. 

Product of NADPH oxidase reaction NADPH provides the reducing equivalents for phagocytes in the process of eliminating invading microorganisms. NADPH oxidase uses molecular oxygen and NADPH to produce superoxide radicals, which in turn can be converted to peroxide, hypochlorous acid, and... 

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