Oxidation/reduction inhibitors

The enzyme 3a-hydroxysteroid dehydrogenase plays a key role in this transport across the hepatocyte. A particularly elegant experiment demonstrated the role of the 3a-hydroxysteroid dehydrogenase, by using [ H] at the 3p hydrogen to show cyclical oxidation-reduction of the 3a-hydroxyl with no accumulation of 3-keto bile acids. Confirmation was obtained by use of indo-methacin, an inhibitor of 3a-hydroxysteroid dehydrogenase, which decreased... 

The acetoxylation reaction is carried out at 70°C under 70 atm pressure by reacting 1,3-butadiene and acetic acid in the presence of air and a small amount of polymerization inhibitor. A special three-step activation (reduction-oxidation-reduction), also used in regeneration of the used catalyst, ensures high activity and selectivity. Regeneration of the catalyst is necessary after about one year of operation. 

Site-specific inhibitors of electron transport shown using a mechanical model for the coupling of oxidation-reduction reactions. [Note Figure illustrates normal direction of electron flow.]... 

Site-specific inhibitors Site-specific inhibitors of electron transport have been identified and are illustrated in Figure 6.10. These compounds prevent the passage of electrons by binding to a component of the chain, blocking the oxidation/reduction reaction. Therefore, all electron carriers before the block are fully reduced, whereas those located after the block are oxidized. [Note Because electron transport and oxidative phosphorylation are tightly coupled, site-specific inhibition of the electron transport chain also inhibits ATP synthesis.]... 

The Fe atoms of the cytochromes undergo oxidation and reduction during respiration, cycling between the ferrous (Fe2+) and ferric (Fe3+) oxidation states. The absorption spectra of the oxidized and reduced forms differ (fig. 14.4). In the 1930s, David Keilin used this property to measure the oxidation-reduction states of cytochromes in living cells. Under anaerobic conditions, the cytochromes rapidly became reduced in the presence of 02, they became oxidized. Certain molecules that inhibited respiration (CO, N3, or CN ) blocked the oxidation other inhibitors (amy-tal, rotenone, and malonate) blocked the reduction. Keilin found that the transfer of electrons from cytochrome c to 02... 

Pace, C. P., and Stankovich, M. T., 1991, Oxidation-reduction properties of trimethylamine dehydrogenase effect of inhibitor binding. Arch. Biochem. Biophys. 287 9711104. 

Methods presently employed for obtaining correctly refolded proteins from inclusion body preparations are often all-or-none propositions. They typically consist of denaturant solubilization, in urea or guanidine, followed by dilution or dialysis (2). Recovery of native activity or structure may be aided by using additives (enzyme inhibitors, co-factors, oxidation-reduction couples, etc.), which act to stabilize the native-state protein conformation. However, because such efforts are time-consuming and tedious, systematic examinations of solution conditions for protein folding/unfolding are rarely performed. 

However, because malonic acid has only one methylene group, it is obvious that no oxidation-reduction can take place. Only association of the enzyme and inhibitor, and dissociation of the I complex, can occur. Another classical example of a competitive inhibitor is the sulfa drug sulfanilamide, which interferes with the biosynthesis of folic acid from the precursor -aminobenzoic acid (PABA). 

The cytochrome P-450 isozymes are a family of microsomal enzymes that collectively have the capacity to transform thousands of different molecules. The transformations include hydroxylations and dealkylations, as well as the promotion of oxidation/reduction reactions. These enzymes have an absolute requirement for NADPH and Oj. The various isozymes have different substrate and inhibitor specificities. 

Prince, R. C., Linkletter, S. J. G., Dutton, P. L., The Thermodynamic Properties of Some Commonly Used Oxidation-Reduction Mediators, Inhibitors and Dyes, as Determined by Polarography", Biochim. Biophys. Acta 635 (1981) 132-148. 

Opine-type secondary amine dicarboxylic acids are useful chiral intermediates of angiotensin-converting enzyme (ACE)-inhibitors, such as enalapril and lysinopril. In order to extend the use of enzymes in stereoselective synthesis, we screened for an enzyme catalyzing the reversible oxidation-reduction of opine-type secondary amine dicarboxylic acids and isolated a bacterial producer, Arthrobacter sp. strain 1C [15]. Optically active secondary amine dicarboxylic acids have been chemically synthesized as... 

Fig. 1 Effect of various agents on the phosphorylation of the B875 complex in chromatophores. Phosphorylation in the presence of (a) 40)LtM DCCD (N,N -Dicyclohexylcarbodiimide, inhibitor of the membrane-bound ATP-ase), (b) 40/im DCCD, (c) 1/iM antimycin A (an inhibitor of electron flow between cytochrome b and cytochrome cl), (d) 100IM antimycin A, (e) 100/iM DBMIB, (f) 5mM Na-ascorbate (a reductant), (g) 5mM Na-dithionite (a strong reductant) and (h) 5mM potassium ferricyanide (an oxidant and inhibitor of electron transport at the reaction center). All samples except (a) contained 2jL6g/ml venturicidin.

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