THE EFFECT OF GLUCOSE ON THE DEVELOPMENT OF RESPIRATION BY ANAEROBICALLY GROWN YEAST.
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Alcohol Oxidoreductases↗
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Hydrogen peroxide is necessary for abscisic acid-induced senescence of rice leaves.
The role of H2O2 in abscisic acid (ABA)-induced rice leaf senescence is investigated. ABA treatment resulted in H2O2 production in rice leaves, which preceded the occurrence of leaf senescence. Dimethylthiourea, a chemical trap for H2O2, was observed to be effective in inhibiting ABA-induced senescence, ABA-increased matondialdehyde (MDA) content, ABA-increased antioxidative enzyme activities (superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase), and ABA-decreased antioxidant contents (ascorbic acid and reduced glutathione) in rice leaves. Diphenyteneiodonium chloride (DPI) and imidazole (IMD), inhibitors of NADPH oxidase, and KCN and NaN3, inhibitors of peroxidase, prevented ABA-induced H2O2 production, suggesting NADPH oxidase and peroxidase are H2O2-generating enzymes in ABA-treated rice leaves. DPI, IMD, KCN, and NaN3 also inhibited ABA-promoted senescence, ABA-increased MDA contents, ABA-increased antioxidative enzyme activities, and ABA-decreased antioxidants in rice leaves. These results suggest that H2O2 is involved in ABA-induced senescence of rice leaves.
Abscisic Acid↗
Oxidation of halides by peroxidases and their subsequent reductions.
The iodide oxidase activity and iodide-dependent pseudocatalatic activity of lignin peroxidase H2, an extracellular enzyme of the white rot fungus Phanerochaete chrysosporium, was inhibited by EDTA. The inhibition of iodide oxidase activity by EDTA was reversed at higher concentrations of iodide. Similar results were observed with a number of peroxidases. On further investigation, it was found that EDTA was decarboxylated in a reaction mixture containing a peroxidase, iodide, H2O2, and EDTA. EDTA was also decarboxylated by hypoiodite, a possible intermediate during oxidation of iodide by peroxidases. Iodide-dependent pseudocatalatic activity was increased with an increase in the concentration of H2O2 and inhibited at higher concentrations of iodide. EDTA was also oxidized by horseradish peroxidase, lactoperoxidase, and myeloperoxidase using iodide or bromide as a mediator. However, only myeloperoxidase was able to decarboxylate EDTA using chloride as a mediator. It is proposed that halide is oxidized to hypohalite by peroxidases. The hypohalite is then reduced by EDTA, H2O2, or halide. Reduction is associated with the decarboxylation of EDTA, oxidation of H2O2 to molecular oxygen, or oxidation of halide.
Agaricales↗
Enzyme electrodes based on organic metals.
The parameters of enzyme electrodes based on organic metals are presented. Cytochrome b2 (E.C. 1.1.2.3), glucose oxidase (E.C. 1.1.3.4), xanthine oxidase (E.C. 1.2.3.2) and peroxidase (E.C. 1.11.1.7) were used in electrodes sensitive to L-lactate, glucose, hypoxanthine and hydrogen peroxide. Electrocatalytic oxidation of NADH on organic metals and ethanol and acetaldehyde sensitive electrodes containing alcohol dehydrogenase (E.C. 1.1.1.1) were studied. Biocatalytic charge accumulation, the mechanism of electron exchange between the enzyme active centres and organic metals, and the future application of organic metals are discussed.
Alcohol Dehydrogenase↗
Purification and characterization of membrane-bound CO-reactive hemoprotein from Tetrahymena pyriformis mitochondria.
A CO-reactive hemoprotein was purified from the mitochondrial membrane fraction of Tetrahymena pyriformis. It showed absorption peaks at 615 and 455 nm in the reduced form and an alpha peak at 565 nm in the pyridine ferrohemochrome spectrum. Although the spectral properties were apparently similar to those of 'cytochrome a620' which was previously proposed as a mitochondrial terminal oxidase in T. pyriformis, it did not contain any molecules of heme a or copper atoms. Further, it showed neither cytochrome c oxidase nor cytochrome c peroxidase activity. These results suggest that 'cytochrome a620' may not be the terminal oxidase in the mitochondrial respiratory chain of T. pyriformis.
Animals↗
Chlorogenic acid as a competitive inhibitor of indoleacetic acid oxidase.
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Acids↗
Inhibition of acyl-CoA oxidase by phenol and its implication in measurement of the enzyme activity via the peroxidase-coupled assay system.
Yeast (Candida tropicalis) acyl-CoA oxidase catalyzes the oxidation of a variety of acyl-CoA substrates to their corresponding alpha-beta enoyl-CoA products, with concomitant reduction of the buffer-dissolved O2 to H2O2. By utilizing indolepropionyl-CoA as a chromogenic substrate, we could measure the enzyme activity either directly by monitoring formation of the reaction product indoleacryloyl-CoA (lambda(max) = 367 nm) or indirectly by measuring the formation of H2O2 via the oxidative-coupled assay system, involving 4-aminoantipyrine, phenol, and horseradish peroxidase. We compared the rates of the enzyme catalysis by the above two methods. The experimental data revealed that the rate measured via the direct method was about twofold higher than that measured by the coupled-assay system. The above difference was found to be due to the inhibition of the enzyme by phenol, one of the reagents of the coupled assay system. The inhibitory role of phenol is not unique for indolepropionyl-CoA as substrate, but is also evident with aliphatic acyl-CoA substrates of varied chain lengths. Since the magnitude of inhibition is dependent on the nature of the acyl-CoA substrate, it is suggested that the coupled-reaction conditions must be carefully standardized with individual substrates. Some tips on standardizing the reaction conditions for quantitative measurement of the acyl-CoA oxidase-catalyzed reaction are offered.
Acyl Coenzyme A↗
Enigmatic Gratuitous Induction of the Covalent Flavoprotein Vanillyl-Alcohol Oxidase in Penicillium simplicissimum.
When Penicillium simplicissimum is grown on veratryl alcohol, anisyl alcohol, or 4-(methoxymethyl)phenol, an intracellular covalent flavin-containing vanillyl-alcohol oxidase is induced. The induction is highest (up to 5% of total protein) during the growth phase. In addition to vanillyl-alcohol oxidase, an intracellular catalase-peroxidase is induced. Induction of vanillyl-alcohol oxidase in P. simplicissimum is prevented by the addition of isoeugenol to veratryl alcohol-containing media, but growth is unaffected. The inhibitory effect of isoeugenol on induction is not observed when anisyl alcohol or 4-(methoxymethyl)phenol is used as the growth substrate. Based on the induction experiments and the degradation pathways for veratryl and anisyl alcohol, we propose that induction of vanillyl-alcohol oxidase is superfluous when P. simplicissimum is grown on these aromatic alcohols. However, the enzyme plays an essential role in the degradation of the methyl ether of p-cresol, 4-(methoxymethyl)phenol.
Journal Article↗
A new peroxidase color reaction: oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with its formaldehyde azine. Application to glucose and choline oxidases.
Hydrogen peroxide in the presence of horseradish peroxidase effects the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone with its formaldehyde azine to form a tetraazapentamethine dye. The blue chromophore, when formed at pH 3.5 and quenched with acetone or 1 N hydrochloric acid, has an extinction coefficient of 69 +/- 2 or 55 +/- 2 mM-1 cm-1, respectively. This chromogen system has been adapted for enzymatic determinations of hydrogen peroxide and of glucose in the 10- to 45-nmol range and of choline in the 5- to 20-nmol range.
Alcohol Oxidoreductases↗
Performance of chloroperoxidase stabilization in mesoporous sol-gel glass using in situ glucose oxidase peroxide generation.
A unique mesoporous sol-gel glass possessing a highly ordered porous structure (with three pore sizes of about 50, 150, and 200 A diameter) was used as a support material for immobilization of the enzyme chloroperoxidase (CPO). CPO was bound onto the glass via a bifunctional ligand, trimethoxysilylpropanal. In situ production of the cosubstrate, H2O2, was achieved using glucose oxidase. Solvent stability in acetonitrile mixtures was enhanced when a pore size larger than the size of CPO was used (i.e., 200 A). From these results, it appears that the glass-enzyme complex developed through the present work can be used as high-performance biocatalysts for various chemical-processing applications, particularly in harsh conditions.
Aldehydes↗
Purification of a new peroxidase catalysing the formation of lignan-type compounds.
A novel peroxidase that catalyses the dimerization of ferulic acid or caffeic acid via oxidative coupling and formation of beta beta'-linkage to the lignan-type compounds 8,8'-bis(caffeic acid) or 8,8'-bis(ferulic acid) respectively was purified from the leaves of Bupleurum salicifolium. The enzyme, for which the name caffeate peroxidase is proposed, was purified 2700-fold. It is a glycoprotein and has an Mr of 38,000 as determined by gel filtration and SDS/PAGE. The Km values for ferulic acid and caffeic acid were 0.24 mM and for H2O2 0.04 mM with caffeic acid and 0.48 mM with ferulic acid. The purified peroxidase does not exhibit activity on other phenylpropanoids tested and has no detectable phenol oxidase or NADPH oxidase activity. The caffeate peroxidase could be involved in the biosynthesis of lignans.
Catalysis↗
Enzymes in dentine and pulp; effect of fluoride.
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Dental Pulp↗
[Nes methods of identification of anti- and pro-oxygenic properties of accessory substances of natural fats].
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Fats↗
Mitochondrial fixation for the detection of cytochrome oxidase activity using microwave irradiation.
We examined cell fixation with microwave irradiation (MWI) used in cytochemistry. MWI was applied to blocks of about 1 mm3 of mouse parotid glands at 500 W for about 5 sec in a fixative at 37 degrees C. The activities of endogenous peroxidase and mitochondrial cytochrome oxidase were demonstrated by using the DAB method with 3,3'-diaminobenzidine (DAB) and 0.01% H2O2. Under electron microscopy, peroxidase activity was localized in the nuclear envelope, endoplasmic reticulum and secretory granules. However, mitochondria cytochrome oxidase activity seemed to be rather weak against the MWI at 37 degrees C. Moreover, suspension of isolated hamster liver mitochondria was fixed by MWI and also demonstrated cytochrome oxidase activity by using the cytochemical methods with DAB, cytochrome c, catalase and sucrose. Such mitochondrial fractions were subjected to 6-second MWI given 10 or 18 times with an interval of 10 seconds with and without a chilled water bath. The final temperature of each fixative was kept at about 10 degrees C or rose to about 37 and 55 degrees C. When we took care to keep the temperature below 10 degrees C, the DAB reaction products accumulated in the mitochondrial intermembrane-intracristal space. No mitochondrial deposits were observed when the temperatures of the fixatives rose to 37 and 55 degrees C. These results indicated that peroxidase was very resistant to the heat with MWI fixation. Cytochrome oxidase is sensitive to the heat with MWI, so, a chilled water bath had to be used.
Animals↗
[Isolation of chitin-specific wheat oxidoreductases].
Anionic peroxidase (IEP approximately 3.5) and oxalate oxidase (IEP approximately 7.0) were isolated from wheat seedlings using chitin. The strength of binding of enzymes with chitin depended on the degree of its acetylation and ionic strength of buffer. It was assumed that the acetyl groups of chitin are involved in sorption of enzymes on this biopolymer. The ability of anionic peroxidase and oxalate oxidase for sorption on chitin allows this biopolymer to be used for isolation of these proteins from plants. Cosorption of anionic peroxidase and oxalate oxidase on chitin suggests that these enzymes cooperate to ensure defensive response of wheat against chitin-containing pathogens.
Adsorption↗
Glutathione dependent control of protein disulfide-sulfhydryl content by subcellular fractions of hepatic tissue.
The disulfide-sulfhydryl (SS/SH) ratios of subcellular fractions of rat hepatic tissue were found to vary diurnally with the ratio lowest in the early morning and highest in the early evening. These changes were found in the nuclear, microsomal and cytosol fractions. The primary reaction is the reversible formation of mixed disulfides of glutathione with proteins. This formation is controlled by the activity of thiol transferase and the level of oxidized glutathione (GSSG) as substrate. Several enzymes including mitochondrial and microsomal oxidases, glutathione reductase and peroxidase and glucose-6-phosphate dehydrogenase were found to control the levels of GSSG. An NADPH-dependent microsomal oxidase system, inhibited by GSSG, was found to produce activated oxygen which served as substrate for flutathione peroxidase. Evidence is presented for the concept that the formation of mixed disulfides of proteins with glutathione is a mechanism for maintenance of a disulfide-sulfhydryl ratio such that the integrity of particulate membranes is maintaine during oxidative and reductive stresses on the hepatic cells.
Animals↗
Studies on a sarcosine oxidase of bacterial origin.
A "sarcosine oxidase" was prepared from a creatinine-decomposing strain of Pseudomonas aeruginosa. The enzyme is inactivated by drying, lyophilization, and dialysis against distilled water. No dialyzable cofactor was found. Optimal activity of the enzyme is reached at pH 7.8. Enzyme activity is directly proportional to enzyme concentration and also to substrate concentration up to the point of saturation of enzyme with substrate molecules. One molecule of enzyme combines with one molecule of substrate. Data concerning the effect of temperature and of a variety of chemical compounds on the enzyme are presented. Its inactivation by heat follows the course of a first order reaction, and the critical thermal increment between 48 degrees and 52 degrees C. was calculated to be 103,000 calories per mol. The relationship of enzyme concentration to heat inactivation rates is illustrated.
Hot Temperature↗
Micro-analytical GO/HRP bioreactor for glucose determination and bioprocess monitoring.
A bi-enzymatic micro-analytical bioreactor integrated in a FIA system for glucose measurements is described. Its robustness and small dimensions (working volume of about 70 microl containing approximately 1.2 mg GO and 0.26 mg HRP) make it easy to operate. The column is based on immobilisation of glucose oxidase (GO) and horseradish peroxidase (HRP) on alkylamine controlled pore glass (CPG) beads. The column has excellent shelf life (no significant loss of activity after 1 year if kept at 4 degrees C), and a very high operational stability that was demonstrated through extensive usage for glucose determinations over 1 year period during which the column retained almost all of its activity. More importantly, this operational stability allows glucose monitoring in the culture media without a decay of signal over the experiment time and consequently no signal correction or re-calibration is needed. This high operational stability was also confirmed by continuous glucose conversion with 30% activity loss after converting quantity of glucose equivalent to 21600 FIA injections of 20 microl with 1.7 mM glucose. Such good performance is a result of an optimised immobilisation method and moreover of the implementation of in situ enzyme stabilisation strategy which consisted on promoting the instantaneous H2O2 consumption produced by the GO. This strategy has the additional advantage of allowing concomitant assay of the H2O2 based on the HAP catalysed co-oxidation of phenol-4-sulphonic acid (PSA) in the presence of 4-aminoantipyrine (4-AAP). The glucose measurements are reproducible with high precision against the standard HPLC method. Linear range and sensitivity depend on sample injection volume; the upper limit is about 1.1 g/l. Lower detection limit is 10mg/l. The column performance has been validated for E. coli and S. cerevisiae fermentation monitoring, and glucose measurements in an animal cell culture (rat Langerhans islets).
Animals↗