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PubMed1979

NADH and NADPH-viologen reductases from Acinetobacter calcoaceticus.

Three pyridine nucleotide-dependent diaphorases have been isolated from Acinetobacter calcoaceticus cells and partially characterized. Two of them, with molecular weights of 165,000 and 57,000, utilize NADPH as electron donor whereas the third one (MW = 57,000) is specific for NADH. Oxidized viologen dyes, flavin nucleotides, dichlorophenol indophenol and ferricyanide can act with efficiency as acceptors in the reaction mediated by these diaphorases. The diaphorase activities have been characterized kinetically, and the effect of different inhibitors and cofactors has been also studied. The diaphorases seem to be subjected to metabolic control by oxidation and reduction.

Acinetobacter↗
PubMedDate not supplied

[Changes in the activity of different classes of enzymes in the cerebral cortex of rats in ontogeny and after the transplantation of embryonic nerve tissue].

The activity of lactate dehydrogenase (LDH), indophenol oxidase, aspartate aminotransferase (AsAT), alkaline phosphatase, acid phosphatase and aldolase at different stages of rat development was measured. We have also determined changes in the activity of these enzymes resulting from transplantation of embryonic nerve tissue (ENT) into the brain of adult animals. During development from the embryo to the adult animal, LDH and AsAT activities increased, while alkaline phosphatase activity diminished. After ENT transplantation, the most prominent changes were in the alkaline phosphatase activity whereas the activity of LDH, AsAT and acid phosphatase remained unchanged and similar to that in the brain cortex of intact adult animals. Changes in the enzyme activity resulting from ENT transplantation changed in a manner characteristic of the transplant. Local brain damage did not change the activity of the studied enzymes fifty days after surgery.

Animals↗
PubMed1990

Enzymatic method for selective determination of 4-aminobenzoic acid in urine.

We developed a method for the selective determination of 4-aminobenzoic acid by use of 4-aminobenzoate hydroxylase (EC 1.14.13.27) to convert 4-aminobenzoic acid to 4-hydroxyaniline. The subsequent conversion of 4-hydroxyaniline to indophenol dye was quantified colorimetrically. The method is reproducible, and the assay response is linear up to 40 mumol/L. Selectivity exceeding that of the current colorimetric assays was demonstrated for these enzymatic determinations of 4-aminobenzoic acid concentrations in urine samples from patients undergoing tests of pancreatic function with bentiromide. This method effectively minimizes interferences from drugs and diet, a problem in current colorimetric methods.

4-Aminobenzoic Acid↗
PubMed1989

[Urease activity of bacteria in urine].

Urea splitting bacteria are related to the formation of struvite or apatite. We investigated the urease activity of bacteria by two methods; the direct measurement of urease activity of viable bacteria and sonicated bacteria from amounts of ammonia by the indophenol method, and the measurement of urease activity by alkalization of infected urine. Proteus mirabilis and Pseudomonas aeruginosa had moderate activity of urease, and Morganella morganii and Staphylococcus epidermidis had the most powerful activity. P. mirabilis caused the strongest alkalization in infected urine.

Humans↗
PubMed1989

Effect of reducing agents and uncouplers on the electrical potential generated by mitochondrial ATPase activity.

Beef heart submitochondrial particles bound to phospholipids impregnated filters generated an electrical potential upon the addition of ATP. The magnitude of the electrical potential reached depended on the phospholipid mixture composition used for filter impregnation, phosphatidylethanolamine being the active component for the electrical potential generation. Uncoupler FCCP (p-trifluoromethoxy carbonyl cyanide phenylhydrazone) inhibited the transmembrane electrical potential generation by diminishing the electrical resistance of the system as a result of its protonophoric action. However, uncouplers 2, 4-dinitrophenol and dicoumarol did not provoke large modifications of the electrical resistance under the conditions of pH and concentration used, and their action varied with the time elapsed after the submitochondrial particles purification, favouring the idea of the uncoupler interaction with a specific site on the membrane. Addition of sodium dithionite resulted in a higher plateau value for the electrical potential consistent with the promoted increase in ATPase activity. The effect of this agent was reversed by the 2,6-dichlorophenol-indophenol added at equivalent concentrations.

Animals↗
PubMed1976

Dependence of starch synthase activity from maize leaves on light, pH and redox state.

The starch synthase activity of bundle sheath cells of maize leaves is very low in darkened plants and increases on illumination. In order to find an explanation of these facts we subjected leaf strips, isolated bundle sheath cells and enzymic preparations to pH-changes and to oxidizing or reducing substances. We found that the increase of the activity produced by light could also be caused in the leaf strips by adding malate to the suspending fluid in the dark. On the contrary, with isolated bundle sheath cells no increase with light or with the addition of malate could be observed. There was a decrease of activity due to acidification or to the addition of dichlorophenol-indophenol (DCPIP). The same effect could be observed with enzymic preparations as with the isolated bundle sheath cells, whereas the decrease of activity was higher by acidification of samples coming from darkened plants than for those enzymes prepared from illuminated plants. Also other substances inhibited the synthase activity: benzoquinone, DOPA, caffeic acid, TMPD or Fe (CN6) 3- and PCMB, while only DTE could increase it. After preincubation with PCMB the enzyme activity could be restored with DTE, not so for the preincubation with DCPIP. With an enzymic preparation that contained intact organelles the increase of activity could also be produced by NADH. Thus we follow that the decrease of synthase activity in the darkened plants is due to acidification and to the presence of oxidizing substances, too.

Glucosyltransferases↗
PubMedDate not supplied

[Enzymatic activity of xenobiotic metabolism in rats with a varying body allowance of vitamin B1].

Vitamin B1 in rats induced in the liver elevation of activity of metabolic enzymes of xenobiotics bound with membranes (dimethylaniline N-demethylase, aniline n-hydroxylase, aryl esterase). At the same time activity of the cytoplasmatic enzymes alcohol dehydrogenase and glutathione-S-transferase was appreciably lowered. An additional load with thiamine (20 mg/kg) led to a drop in activity of the membrane-bound enzymes. Vitamin B1 deficiency modified the effect of the inductor phenobarbital. Additional administration of vitamin B1 to thiamine-deficient animals normalized the thiamine level in the liver, and activity of hydroxylase, aryl esterase, formaldehyde dehydrogenase, and significantly decreased demethylase activity. In vitamin B1-deficient animals high detergent concentrations significantly suppressed NADH-dichlorophenol-indophenol-reductase activity, while low concentrations activated this enzyme as compared to the control.

Animals↗
PubMed1985

Principal component analysis for a better understanding of the herbicidal effectivity of some benzonitriles.

To gain more insight in mode of action of ten different 4-hydroxy-benzonitrile derivatives, their biological activities in eight bioassays, and their lipophilicity and adsorptivity determined by thin-layer chromatography in nine different systems were subjected to principal component analysis. Four background components explained about 90% of total variance. Only three of eight biological activities, the inhibition of the 2,6-dichlorophenol-indophenol reduction by spinach and wheat chloroplasts and the CO2 fixation of wheat seedlings had not any common background components with the physico-chemical parameters of the compounds. The nonlinear mapping of principal component loadings and variables showed, that the in vivo and in vitro biological activities differed considerably and depended on the object investigated. The effectivity of compounds is governed mainly by the number of substituents and by the presence of free hydroxy group.

Chromatography, High Pressure Liquid↗
PubMed1979

Arylesterase in serum: elaboration and clinical application of a fixed-incubation method.

A sensitive, specific, and simple method for determining serum or urine arylesterase (EC 3.1.1.2) is described. The enzyme acts on phenyl acetate to release phenol, which produces a stable indophenol dye with 4-aminoantipyrine and potassium ferricyanide. Arylesterase, a thiol enzyme, is reactivated by 2-mercaptoethanol and by cysteine, but not by reduced glutathione. Calcium is indispensable to stabilize and to activate (Km = 0.85 mmol/L) the enzyme; complete protection is achieved at CaCl2 20 mmol/L. Magnesium acts as a weak (Ki = 116 mmol/L), lanthanum as a potent (Ki = 5 mumol/L) competitive inhibitor. The activity is measured in diluted sera at phenyl acetate 4.0 mmol/L (Km = 1.12 mmol/L), pH 7.8 and 25 degrees C. The normal range extends from 53 to 186 kU/L, and four isoenzymes are present in sera from healthy adults. Arylesterase decreases in hepatic disorders, especially in cirrhosis and carcinoma of the liver, with reduction of the penultimate fraction in polyacryalmide gel electrophoresis.

Adolescent↗
PubMed1979

Chemical inhibition used in a kinetic urease/glutamate dehydrogenase method for urea in serum.

We describe a fixed-time-interval, kinetic inhibition method, with use of a competitive inhibitor (l) of the urease/glutamate dehydrogenase reaction to increase the "apparent" Michaelis constant by a factor of (1 + [l]lKl). This allows greater flexibility in selecting an appropriate sample dilution for kinetic determinations of urea in serum (i.e., [S]lKm ratio). Nine compounds were screened as potential inhibitors for this study. Adding 5 mmol of hydroxyurea per liter increases the "apparent" Michaelis constant for the coupled enzyme reaction by 10-fold. We used a sample dilution of 21-fold vs. dilutions of 141- to 350-fold for previously reported kinetic methods. Mean analytical recovery with this method was 100.2%. Reaction rate vs. urea concentration was linear, and complete recovery extended to 30 mmol of urea per liter. Of 22 potential interferents, only fluoride (250 mmol/L) and bilirubin (1 mmol/L, or 580 mg/L) caused greater than 5% interference. We discuss precision and effects of specimen dilution, and compare results for 100 specimens with those by a manual Berthelot-indophenol method, a manual diacetyl monoxime method, and a diacetyl monoxime method adapted to continuous-flow analysis.

Autoanalysis↗
PubMed1981

Effect of lipids on a membrane-bound NADH dehydrogenase from Bacillus caldotenax.

NADH dehydrogenase [EC 1.6.99.3] in membranes of Bacillus caldotenax was solubilized with sodium N-lauroylsarcosinate and purified 50-fold from membranes to 75-80% homogeneity, as judged by SDS-polyacrylamide gel electrophoresis. The enzyme was considered to be located on the electron transport chain and to be an FAD-containing protein. The molecular weight of the subunit was estimated to be 44,000. The enzyme (or the enzyme bound to the B. caldotenax membrane lipids) follows a ping-pong mechanism. The enzyme can oxidize NADH, but not NADPH, with 2,6-dichlorophenol indophenol, ferricyanide, menadione, and cytochrome c as electron acceptors. Membrane lipids or Triton X-100 stimulated the enzyme activity, except that with menadione. Lipids decreased the apparent affinity of electron acceptors and NADH to the enzyme, and increased the maximum velocity, except when menadione was used as the electron acceptor. Lipids partially protected the enzyme from thermal inactivation. The enzyme exhibited a continuous Arrhenius plot, while the lipids- or membrane-bound enzyme exhibited a discontinuous plot.

Bacillus↗
PubMed1983

Oxidation of p-aminophenol catalyzed by horseradish peroxidase and prostaglandin synthase.

p-Aminophenol oxidation is catalyzed by horseradish peroxidase. ESR spectroscopy demonstrates the formation of the p-aminophenoxy free radical, the one-electron oxidation product of p-aminophenol. The same radical is formed by alkaline autoxidation of this compound. The ultimate products of p-aminophenol oxidation are mainly polymeric; however, indophenol was isolated in low yield. Oxidation of p-aminophenol is also catalyzed by the hydroperoxidase activity of prostaglandin synthase, using ram seminal microsomal preparations as the enzyme source.

Aminophenols↗
PubMed1984

Quantitation of the rapid electron donors to P700, the functional plastoquinone pool, and the ratio of the photosystems in spinach chloroplasts.

Recent studies of chloroplast architecture have emphasized the segregation of photosystem I and photosystem II in different regions of the lamellar membrane. The apparent localization of photosystem II reaction centers in regions of membrane appression and of photosystem I reaction centers in regions exposed to the chloroplast stroma has focused attention on the intervening electron carriers, carriers which must be present to catalyze electron transfer between such spatially separated reaction sites. Information regarding the stoichiometries of these intermediate carriers is essential to an understanding of the processes that work together to establish the mechanism and to determine the rate of the overall process. We have reinvestigated the numbers of photosystem I and photosystem II reaction centers, the numbers of intervening cytochrome b6/f complexes, and the numbers of molecules of the relatively mobile electron carriers plastoquinone and plastocyanin that are actively involved in electron transfer. Our investigations were based on a new experimental technique made possible by the use of a modified indophenol dye, methyl purple, the reduction of which provides a particularly sensitive and accurate measure of electron transfer. Using this dye, which accepts electrons exclusively from photosystem I, it was possible to drain electrons from each of the carriers. Thus, by manipulation of the redox condition of the various carriers and through the use of specific inhibitors we could measure the electron storage capacity of each carrier in turn. We conclude that the ratio of photosystem I reaction centers to cytochrome b6/f complexes to photosystem II reaction centers is very nearly 1:1:1. The pool of rapid donors of electrons to P700 includes not only the 2 reducing equivalents stored in the cytochrome b6/f complex but also those stored in slightly more than 2 molecules of plastocyanin per P700. More slowly available are the electrons from about 6 plastoquinol molecules per P700.

Chlorophyll↗
PubMed1984

[Method for the photometric determination of aldehyde oxidase activity].

A method has been developed for the determination of aldehyde oxidase. Dimethylaminocinnamaldehyde was taken as substrate. It is oxidized to the corresponding acid and changes ist absorption at 398 nm. Except dissolved oxygen no additional electron acceptor is needed. This alternative assay was found to be about twice as sensitive compared to the method with acetaldehyde and dichlorophenol indophenol. Aldehyde oxidase activity was estimated in the raw extract of livers of pig, sheep and rat. Xanthine oxidase does not interfere.

Aldehyde Oxidase↗
PubMed1984

Selenite binding to carbon monoxide oxidase from Pseudomonas carboxydovorans. Selenium binds covalently to the protein and activates specifically the CO----methylene blue reaction.

The CO----methylene blue and CO----dichlorophenol indophenol activities of carbon monoxide oxidase were specifically activated upon aerobic incubation with selenite, whereas the NADH----methylene blue activity was not altered. Fully active enzyme contained selenium, molybdenum, and flavin adenine dinucleotide in a 1:1:1 ratio. Selenium was covalently bound to the protein, probably between the sulfurs of half-cystine residues, and not a constituent of the molybdenum cofactor. The action of selenite was directed to the cytoplasmic species of carbon monoxide oxidase exclusively, whereas the CO----methylene blue activity of the membrane-bound enzyme remained unaffected.

Aldehyde Oxidoreductases↗
PubMed1983

Properties of NADH-cytochrome-b5 reductase from human neutrophils.

An NADH-ferricyanide reductase activity of ca. 170 nmole ferricyanide reduced/min/10(7) cells is present in the membrane fraction of human neutrophils. This membrane-bound activity constitutes ca. 85% of the total NADH-ferricyanide reductase activity that is present in these cells. The enzyme(s) readily utilize(s) purified cytochrome-b5 from beef liver as an electron acceptor. No other physiologic electron acceptors tested (e.g., ubiquinone-30, menadione) were active. The specificities of electron donors (e.g., NADH congruent to deamino-NADH much greater than NADPH) and acceptors (e.g., Fe(CN)6-3 greater than 2,6-dichlorophenol-indophenol much greater than O2) for the enzyme(s) in unfractionated membranes, along with action of inhibitors (e.g., ADP, p-chloromercuribenzoate) and the pH optimum, indicate that virtually all of the membrane-bound ferricyanide reductase activity in these cells is NADH-cytochrome-b5 reductase. This reductase, however, is only slightly solubilized (ca. 10%) by a phosphate buffer extraction procedure that is effective with the liver enzyme.

Adenine Nucleotides↗
PubMed1983

Simultaneous determination of protein (nitrogen), phosphorus, and calcium in animal feedstuffs by multichannel flow-injection analysis.

A 3-channel flow-injection procedure was developed, which enables the simultaneous determination of protein, phosphorus, and calcium in a wide range of animal feeds from a single digestion. Samples are digested with a block digestor, diluted, and analyzed at a rate of 82 samples/h. Protein (nitrogen) as ammonia is determined colorimetrically by the indophenol method. Phosphorus and calcium are determined by measuring the absorbances of the molybdenum blue and calcium-cresolphthalein complexes at 660 and 580 nm, respectively. Protein is determined in the range from 0 to 75%, phosphorus in the range from 0 to 6%, and calcium in the range from 0 to 6%. The results obtained do not differ significantly from those obtained by proven manual methods, and considerable time, space, and reagents are saved.

Animal Feed↗
PubMed1978

Emergency determination of acetaminophen.

I describe a senstive colorimetric micromethod in which a pH 11.0 carbonate buffer is used to induce acetaminophen to react with Folin-Ciocalteau reagent at room temperature. These reagents and a simple solvent extraction favor formation of a stable indophenol dye with acetaminophen, giving this procedure a good degree of specificity. Results correlate well with those by liquid-chromatographic procedures, and day-to-day precision is less than 8%.

Acetaminophen↗