Cytochrome reaction kinetics

Several enzymes have been immobilized in sol-gel matrices effectively and employed in diverse applications. Urease, catalase, and adenylic acid deaminase were first encapsulated in sol-gel matrices [72], The encapsulated urease and catalase retained partial activity but adenylic acid deaminase completely lost its activity. After three decades considerable attention has been paid again towards the bioencapsulation using sol-gel glasses. Braun et al. [73] successfully encapsulated alkaline phosphatase in silica gel, which retained its activity up to 2 months (30% of initial) with improved thermal stability. Further Shtelzer et al. [58] sequestered trypsin within a binary sol-gel-derived composite using TEOS and PEG. Ellerby et al. [74] entrapped other proteins such as cytochrome c and Mb in TEOS sol-gel. Later several proteins such as Mb [8], hemoglobin (Hb) [56], cyt c [55, 75], bacteriorhodopsin (bR) [76], lactate oxidase [77], alkaline phosphatase (AP) [78], GOD [51], HRP [79], urease [80], superoxide dismutase [8], tyrosinase [81], acetylcholinesterase [82], etc. have been immobilized into different sol-gel matrices. Hitherto some reports have described the various aspects of sol-gel entrapped biomolecules such as conformation [50, 60], dynamics [12, 83], accessibility [46], reaction kinetics [50, 54], activity [7, 84], and stability [1, 80],... 

In order to obtain further information on the magnitude of the overall reaction volume and the location of the transition state along the reaction coordinate, a series of intermolecular electron-transfer reactions of cytochrome c with pentaammineruthenium complexes were studied, where the sixth ligand on the ruthenium complex was selected in such a way that the overall driving force was low enough so that the reaction kinetics could be studied in both directions (153, 154). The selected substituents were isonicotinamide (isn), 4-ethylpyr-idine (etpy), pyridine (py), and 3,5-lutidine (lut). The overall reaction can be formulated as... 

Chance, B. Devault, D. (1964) Kinetics and quantum efficiency of the chlorophyll-cytochrome reaction, Per. Bunsenges. Physik. Chem. 68, 722-726. 

Harris, T. K., and Davidson, V. L., 1993b, Binding and electron transfer reactions between methanol dehydrogenase and its physiologic electron acceptor cytochrome C55jjOa kinetic and thermodynamic analysis. Biochemistry 32 14145nl4150. 

Fig. 5. Comparison of kinetics of cytochrome oxidation and reduction in an anaerobic suspension of intact ceils of the photosynthetic bacterium Chromatium at 300,250 and 77 K. Scaies for the absorbance-change and time as well as the calculated rates of cytochrome oxidation and re-reduction are shown. Figure source left panel from Chance and Nishimura (1960) On the mechanism of chiorophyil-cytochrome interaction The temperature insensitivity of tight-induced cytochrome oxidation in Chromatium. Proc Nat Acad Sci, USA. 46 20 and right panei from Chance and DeVault (1964) On the kinetics and quantum efficiency of the chiorophyil-cytochrome reaction. Ber Bunsenges Phys Chem 68 725.

Fig. 6. Temperature dependence of the rates of cytochrome oxidation in Chromatium ceils induced by 10-ns ( ) and 0.5-ms ( ) laser flashes. The numbers beside the data points are the number of observations averaged into one data point. Reproduced from DeVault and Chance (1966) On the kinetics and quantum efficiency of the chlorophyll-cytochrome reaction. Biophys J 6 832.

B Chance and D DeVault (1964) On the kinetics and quantum efficiency of the chiorophyii-cytochrome reaction. Ber Bunsenges Phys Chem 68 723-726... 

Schindler, F. (1964), Reaction Kinetics of the Cytochrome Oxidase, Ph.D. Dissertation, University of Pennsylvania. 

Several reports have evaluated the homogeneous electron transfer kinetics of cytochrome c using potential step spectroelectrochemistry. These reports together with other studies of biological homogeneous electron transfer reaction kinetics are summarized in Table 3. Evaluation of the kinetics of these reactions requires caution in that the small diffusion coefficients of the biological molecules studied relative to those of the electrochemically generated reactants mandates consideration of these parameters in data analysis. ... 

Griffin BW, Peterson JA (1972) Camphor binding of Pseudomonas putida cytochrome P450. Kinetics and thermodynamics of the reaction. Biochemistry 11 4740 746... 

Matsunaga I, Yamada A, Lee DS, Obayashi E, Fuji-wara N, Kobayashi K, Ogura H, Shiro Y (2002) Enzymatic reaction of hydrogen peroxide-dependent peroxygenase cytochrome P450s kinetic deuterium isotope effects and analyses by resonance Raman spectroscopy. Biochemistry 41 1886-1892... 

Cyclic voltammetry and other electrochemical methods offer important and sometimes unique approaches to the electroactive species. Protein organization and kinetic approaches (Correia dos Santos et al. 1999, Schlereth 1999) can also be studied by electrochemical survey. The electron transfer reaction between cytochrome P450scc is an important system for... 

Figure 26 shows the redox potential of 40 monolayers of cytochrome P450scc on ITO glass plate in 0.1 KCl containing 10 mM phosphate buffer. It can be seen that when the cholesterol dissolved in X-triton 100 was added 50 pi at a time, the redox peaks were well distinguishable, and the cathodic peak at -90 mV was developed in addition to the anodic peak at 16 mV. When the potential was scanned from 400 to 400 mV, there could have been reaction of cholesterol. It is possible that the electrochemical process donated electrons to the cytochrome P450scc that reacted with the cholesterol. The kinetics of adsorption and the reduction process could have been the ion-diffusion-controlled process. 

C. Shen and N.M. Kostic. Kinetics of photoinduced electron-transfer reactions within sol-gel silica glass doped with zinc cytochrome c. Study of electrostatic effects in confined liquids. J. Am. Chem. Soc. 119, 1304-1312 (1997). 

D.R. McMillin, Purdue University In addition to the charge effects discussed by Professor Sykes, I would like to add that structural effects may help determine electron transfer reactions between biological partners. A case in point is the reaction between cytochrome C551 and azurin where, in order to explain the observed kinetics, reactive and unreactive forms of azurin have been proposed to exist in solution (JL). The two forms differ with respect to the state of protonation of histidine-35 and, it is supposed, with respect to conformation as well. In fact, the lH nmr spectra shown in the Figure provide direct evidence that the nickel(II) derivative of azurin does exist in two different conformations, which interconvert slowly on the nmr time-scale, depending on the state of protonation of the His35 residue (.2) As pointed out by Silvestrini et al., such effects could play a role in coordinating the flow of electrons and protons to the terminal acceptor in vivo. 

CL reaction can be catalyzed by enzymes other than HRP (e.g., microperoxidase and catalase) and by other substances [hemoglobin, cytochrome c, Fe(III), and other metal complexes]. The presence of suitable molecules such as phenols (p-iodophenol), naphthols (l-bromo-2-naphthol), or amines (p-anisidine) increases the light production deriving from the HRP-catalyzed oxidation of luminol and produces glow-type kinetics [6, 7], The use of other enzymes, such as glucose-6-phosphate dehydrogenase [38-41], P-galactosidase [42], and xanthine oxidase [43-46], as CL labels has been reported. 

The kinetics of reactions of NO with ferri- and ferro-heme proteins and models under ambient conditions have been studied by time-resolved spectroscopic techniques. Representative results are summarized in Table I (22-28). Equilibrium constants determined for the formation of nitrosyl complexes of met-myoglobin (metMb), ferri-cytochrome-c (Cyt111) and catalase (Cat) are in reasonable agreement when measured both by flash photolysis techniques (K= konlkQff) and by spectroscopic titration in aqueous media (22). Table I summarizes the several orders of magnitude range of kon and kQs values obtained for ferri- and ferro-heme proteins. Many k0f[ values were too small to determine by flash photolysis methods and were determined by other means. The small values of kQ result in very large equilibrium constants K for the... 

Similar results were obtained for the redox reactions of a series of cobalt diimine complexes with cytochrome c (156, 157). In general a good agreement exists between the kinetically and thermodynami-... 

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