Catalase inhibition

Catalase inhibition. Water extract of the fresh root, administered intragastrically to infant mice at a dose of 50 mL/kg, was active. The treatment was administered for seven successive days, followed by a single dose of 20% v/v CCI4 in olive oil subcutaneously at 1 mL/kg on the last day 1 hour after the administration of the carrot extract " . Chloroform-methanol (9 1) fraction of the ethanol (95%) extract, ethyl acetate fraction of the water extract, and chloroform-soluble fraction of the water extract of the seed were active on the nonpregnant rat uterus° L... 

However, when PMNs were stimulated, not by antibody on the surface of the tumor cell, but instead by Concanavalin Aor by opsonized zymosan myeloperoxidase did appear to mediate the killing azide and cyanide inhibited the killing, halides were required, catalase inhibited, and PMNs from patients with either hereditary deficiency of myeloperoxidase or chronic granulomatous disease were... 

Cathodic reduction of molecular oxygen affords H02 , which also can replace NADH + 02 to activate P 450, and the oxidative demethyl-ation ofp-anisole was catalyzed effectively by the P-450-HO2 system (18). Addition of catalase inhibited the demethylation, demonstrating that H02 was the activating species. 

Pedraza-Chaverri J, Granados-Silvestre MA, Medina-Campos ON, Hernandez-Pando R (1999) Effect of the in vivo catalase inhibition on aminonucleoside nephrosis. Free Rad Biol Med 27 245-253... 

All three ingredients were necessary for radical formation. Hydrogen peroxide greatly enhanced the yield, whilst catalase inhibited the OH adduct formation. The system was able to induce the oxidation of ethanol, and reaction rates agreed with those expected for OH radical attack. 

The exact mechanism of aminoglycoside nephrotoxicity is unclear. As discussed above, release of lysosomal enzymes can contribute to altered cellular function. Hydroxy radicals may also play a role in aminoglycoside mitochondrial effects, since catalase inhibits in vitro alterations of mitochondrial function by gentamicin and the use of hydroxy radical scavengers or iron chelators reduces gentamicin nephrotoxicity in vivo. Additionally,... 

Studies on nitrosylation reactions of metalloporphyrins are emerging and have been reviewed. 21 Reactions involving FeNO 7 and FeNO 6 species (considered as ferroheme and ferriheme, respectively) are crucial to enzymatic functions (activation of guanylyl cyclase, cytochrome oxidase, catalase inhibition). Reversible photodissociations of NO from nitrosyl metalloporphyrins have been studied by ns-pulsed laser techniques, providing values for kt and kA (Equation (12)). Dissociation processes are very slow, particularly for ferroheme complexes however, kA values in the 10-5—101 s 1 range have been measured for several five-coordinated FeNO 7 tetraarylpor-phyrins.103 The spread in the kA values is not well understood yet. 

In methylotrophic yeast with peroxisomal damage induced by peroxisomicine A, A2 and tullidinol no evidence of catalase inhibition was seen, either. Considering these results, it has been suggested that catalase is not directly involved in the selective effect of these compounds on peroxisomes. 

Endogenous formation of reactive oxygen species was markedly increased in catalase-inhibited or GSH-depleted isolated rat hepatocytes (Siraki et al. 2002). Respiratory chain inhibitors or hypoxia markedly increased the formation of reactive oxygen species before cytotoxicity ensued. 

Cadenas, 8., Rojas, C., Perez-Campo, R., L6pez-Torres, M., and Barja, G., 1994a, Effect of dietary vitamin C and catalase inhibition on antioxidants and molecular markers of oxidative damage in guinea pigs, Free Rad. Res. 21 109-118. 

The first actual demonstration of an enzyme-substrate compound of catalase and ethyl hydrogen peroxide was made in 1935 by Stem (329) by a rapid spectrophotographic method, but it was found later that Stern had observed an inactive complex at that time. George (158), in 1947, demonstrated the reversibility of the catalase inhibition on diluting the solution. Ogura et al. (257) postulated a tjrpe of ES complex similar to that of Lineweaver and Burk, but could not obtain direct experimental evidence for its existence. Finally, Chance (92) identified a red inactive enz5une-substrate complex and measured its properties. He was able to demonstrate experimentally that this complex had properties different from those of the inactive ES complexes observed earlier. 

The success of the titrimetrie method rests upon several conditiems (a) the reaction time should be short (b) the H2O2 concentration should be low (c) the reaction mixture should be suitably buffered as in the gas-ometric technique and (d) in addition, small volumes (to reduce catalase inhibition by dilution and adsorption) as well as low temperatures are desirable but not essential. 

Tanaka and Knox (40) have recently found that peroxide is not directly involved in the formation of formylk3Tiurenine, but acts in converting an inactive ferric enzyme in the presence of tryptophan into an active ferrous protein. It is of interest that cyanide and catalase inhibit the inactive enzyme but not the active ferrous form. On the other hand, carbon monoxide inhibits only the active enzyme. The changes have been summarized by Tanaka and Knox according to the scheme given in Fig. 3. These authors have suggested, since the reaction involves a direct oxygenation of the substrate, that the enzyme be termed tryptophan pyrrolase rather than the previously used nomenclature of tryptophan-peroxidase-oxidase. 

Administered at 1.25% and 2.5% of the diet of female rats subjected to carcinogen-induced mammary carcinogenesis, asafetida increased activity levels of endogenous antioxidants (glu-tathione-5-transferase, reduced glutathione, superoxide dismutase, and catalase), inhibited lipid peroxidation, delayed tumor appearance, and reduced the size of tumors. The essential oil showed a relaxant effect on isolated rat ileum. Asafetida has also shown hypotensive activities in animals. It has also been demonstrated to increase blood coagulation time. ... 

During the operation of glycolate oxidase in normal photorespiration, hydrogen peroxide is formed and is removed by peroxisome-based catalase. The potential toxic action of hydrogen peroxide has already been discussed, and the herbicidal action of aminotriazole is assumed to be, in part, due to catalase inhibition.Mutants of barley that are catalase deficient are rapidly bleached in normal air, in which photorespiration may operate, but will grow normally under C02-enriched air. " It is of interest that in this barley mutant and also in aminotriazole-treated plants, there was an enhancement in the level of leaf glutathione, probably due to increased pressure upon radical-scavenging systems. 

Tryptophan oxygenase (tryptophan pyrrolase) plays an important role in the metabolism of tryptophan and has been prepared from animal tissues (Knox and Mehler, 1950) and bacteria (Hayaishi and Stanier, 1951). Enzymes from the two sources were found to be comparable in many respects. Knox and Mehler named the enzyme tryptophan peroxidase-oxidase, since they had found that catalase inhibits the reaction and that this inhibition is reversed by hydrogen peroxide, suggesting the intermediate formation and the subsequent utilization of peroxide as shown in Eqs. (21) and (22). 

The resemblance between the model hydroxylating system of Uden-friend and the phenolase plus ascorbic acid system is real, as in both cases probably free radicals and certainly hydrogen peroxide are formed. The steady state concentration of the hydrogen peroxide is much higher in the former than in the latter system, and this difference alone can of course explain the fact that the catalase inhibits the hydroxylation... 

Mason (1957) offered an alternative explanation of the catalase inhibition. He suggested that complexes 2 and 3 may be decomposed by this enzyme. 

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