Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:O95477 (membrane-bound)
 29,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A monooxygenase isolated from 5-day old etiolated Vinca rosea seedlings was shown to catalyze the hydroxylation of the monoterpene alcohols, geraniol and nerol, to their corresponding 10-hydroxy derivatives. Hydroxylase activity was inpendent upon NADPH (neither NADH nor combination of NADH, NADP+ and ATP served as substitutes) and O2. Geraniol hydroxylation was enhanced by dithiothreitol (monothiols were less effective) and inhibited by phospholipases, thiol reagents, metyrapone, and cytochrome c, as well as other inhibitors of cytochrome P-450 systems. Geraniol was hydroxylated at a faster rate than nerol, but the alcohols possessed similar apparent Km values. The membrane-bound hydroxylase was solubilized by treatment with sodium cholate, Renex-30, or Lubrol-WX. Cholate-treated enzyme was resolved by DEAE-cellulose chromatography and reconstitution of the hydroxylase was effected utilizing different fractions containing cytochrome P-450, a NADPH-cytochrome c reductase, and lipid.
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PMID:Characterization of a cytochrome P-450 dependent monoterpene hydroxylase from the higher plant Vinca rosea. 0 9

Membrane vesicles can be prepared from murine lymphoid cells by nitrogen cavitation and fractionated by sedimentation through nonlinear sucrose density gradients. Two subpopulations of membrane vesicles, PMI and PMII, can be distinguished on the basis of sedimentation rate. The subcellular distribution of adenylate and guanylate cyclases in these membrane subpopulations have been compared with the distribution of a number of marker enzymes. Approximately 20-30% of the total adenylate and guanylate cyclase activity is located at the top of the sucrose gradient (soluble enzyme), the remainder of the activity being distributed in the PMI and PMII fractions (membrane-bound enzyme). More than 90% of the 5'-nucleotidase and NADH oxidase activities detected in lymphoid cell homogenates are located in PMI and PMII fractions, whereas succinate cytochrome c reductase activity is detected only in the PMII fractions. In addition, beta-galactosidase activity is distributed in the soluble and PMII fractions of the sucrose density gradients. On the basis of the fractionation patterns of these various enzyme activities, it appears that PMI fractions contain vesicles of plasma membrane and endoplasmic reticulum, whereas PMII fractions contain mitochondria, lysomes, and plasma membrane vesicles. Approximately 30-40% of the adenylate and guanylate cyclase activities in PMII can be converted to a PMI-like form following dialysis and resedimentation through a second nonlinear sucrose gradient. Adenylate and guanulate cyclases can be distinguished on the basis of sensitivity to nonionic detergents.
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PMID:The subcellular distribution of adenylate and guanylate cyclases in murine lymphoid cells. 0 90

The purified respiratory chain NADH dehydrogenase of Escherichia coli oxidizes NADH with either dichlorophenolindophenol (DCIP). ferricyanide, or menadione as electron acceptors, with values for NADH are similar with the three electron acceptors (approximately 50 muM). The purified enzyme contains no flavin and has an absolute requirement for FAD, with Km values around 4 muM. The pH optimum of the enzyme appears to be between 6.5 and 7; the optimum is difficult to establish because of nonenzymatic reduction of DCIP at the lower pH values. Potassium cyanide stimulates the DCIP reductase activity about 2-fold, but has no effect on ferricyanide reductase. The enzyme exhibits hyperbolic kinetics with respect to NADH concentration in both the ferricyanide and DCIP reductase assays, but cooperatively is seen in the menadione reductase reaction. NAD+ is an effective competitive inhibitor of the reaction (Ki congruent to 20 muM); in the presence of NAD+, the NADH saturation curve becomes cooperative, even in the DCIP reductase assay. Many adenine containing nucleotides are competitive inhibitors of the enzyme. The apparent Ki values for these nucleotides as inhibitors of the purified enzyme, the membrane-bound NADH dehydrogenase, and the NADH oxidase are equivalent. An examination of inhibitory effects of a series of adenine nucleotides suggests that the inhibitors act as analogues of NAD+, which is the true physiological inhibitor. The results suggest that the enzyme in situ is always partially inhibited by the levels of NAD- in the E coli cell, and thus behaves in a cooperative fashion to changes in the NAD+/NADH ratio. An antibody has been elicited against the purified NADH dehydrogenase. Immunodiffusion and crossed immunoelectrophoresis show that the antibody is directed principally against the NADH dehydrogenase, with some activity against minor contaminants in the purified preparation. The antibody inhibits NADH dehydrogenase activity 50% at saturating levels. When this antibody preparation is used to examine solubilized membrane preparations, two major immunoprecipitates are found. A parallel inhibition of the membrane-bound NADH dehydrogenase and NADH oxidase activities is seen, supporting the hypothesis that the purified enzyme is indeed a component of the respiratory chain-dependent NADH oxidase pathway.
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PMID:The NADH dehydrogenase of the respiratory chain of Escherichia coli. II. Kinetics of the purified enzyme and the effects of antibodies elicited against it on membrane-bound and free enzyme. 0 8

The properties of the membrane-bound reduced nicotinamide adenine dinucleotide (NADH) oxidase of Acholeplasma laidlawii were compared with those of the corresponding cytoplasmic activity of Mycoplasma mycoides subsp. capri. The striking differences in pH optima, susceptibility to inhibitors and detergents, and heat inactivation between the NADH oxidase activity, with oxygen as an electron acceptor, and the NADH oxidoreductase activity, with dichlorophenol indophenol (DCPIP) as an alternate electron acceptor, support the presence of more than one catalytic protein in both the membrane-bound and soluble enzyme systems. The detection of more than one band positive for the NADH-nitroblue tetrazolium oxidoreductase reaction on electrophoresis of either the membranes of A. laidlawii or the cytoplasm of M mycoides subsp. capri also points in the same direction. The membrane-bound enzyme system differed, however, form the soluble one because it had a lower ratio of oxidase activity to oxidoreductase activity, and because it was less susceptible to heat inactivation and more readily incorporated incorporated into reaggregated membranes. In addition, the specific activity of the membrane-bound enzyme system increased as the culture aged, whereas that of the soluble system decreased as the culture aged. It is suggested that the different location in the cell could be responsible for some of the differences between the membrane-bound NADH oxidase activity of A. laidlawii and that found in the cytoplasm of M. mycoides subsp. capri.
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PMID:Reduced nicotinamide adenine dinucleotide oxidase activity in membranes and cytoplasm of Acholeplasma laidlawii and Mycoplasma mycoides subsp. capri. 1 Dec 8

The NADH: (acceptor) oxidoreductase (EC 1.6.99.3) was isolated from human erythrocyte ghosts by a procedure including Triton X-100 solubilization, affinity chromatography on an NAD+-Sepharose 4B column, ammonium sulfate precipitation, and isoelectric focusing. This enzyme preparation was characterized by a single band on the urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by a single precipitin line with its corresponding antiserum on double diffusion and immunoelectrophoresis. A 103-fold purification indicates that the oxidoreductase represents approximately 1% of the ghost protein mass. The specific activity of the purified enzyme was 112 units/mg protein. The pH optimum was 6.8 and the isoelectric point, pI, was 6.6 The oxidoreductase has a specificity for NADH as a cofactor. The NADPH was ineffective as a reducing agent. The enzyme activity was strongly temperature-dependent, displaying maximal activity between 35 and 40 degrees C. The energy of activation was 4.9 kcal. The enzyme activity was inhibited by sulfhydryl reagents, anionic detergents, and divalent ions. The amino acid composition of the purified enzyme is characterized by the presence of all common amino acids including half-cystine and tryptophan. The results of carbohydrate and lipid analyses indicated that the oxidoreductase is a glycolipoprotein with fucose, galactose, mannose, and glucosamine as the sugar components and cholesterol and sphingomyelin as the lipid constituents. The apparent subunit molecular weight estimated by urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence and presence of 2-mercaptoethanol was 40,000. The antiserum completely inhibited the enzymic activity at the equivalence point. We suggest that the membrane-bound NADH: (acceptor) oxidoreductase might be a transmembrane protein.
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PMID:Isolation and partial characterization of human erythrocyte membrane NADH: (acceptor) oxidoreductase. 3 37

A b-type cytochrome and NADH-ferricyanide (FC) reductase were solubilized from Ascaris muscle microsomes by detergents and purified by column chromatography. The purified b-type cytochrome displayed absorption bands at 560 (alpha-peak), 525 (beta-peak), and 424 nm (gamma-peak), with a marked shoulder at 555 nm in the reduced from, 415 nm (gamma-peak) in the oxidized form. This absorption spectrum was different from that of rat liver microsomal cytochrome b5. The molecular weight was estimated to be about 100,000 by SDS-polyacrylamide gel electrophoresis, and the absorption spectrum of alkaline pyridine ferrohemochrome suggested that the prosthetic group of this cytochrome is protoheme. The molecular weight of the purified NADH-FC reductase was estimated to be about 55,000 by SDS-polyacrylamide gel electrophoresis. The purified reductase required NADH as a specific electron donor. The reductase efficiently reduced some redox dyes with NADH, but the reduction of cytochrome c was much slower. The purified reductase, like the membrane-bound reductase, was not inhibited by thiol reagents.
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PMID:Biochemical studies on the muscle microsomes of Ascaris lumbricoides var. suum. II. Purification and characterization of b-type cytochrome and NADH-ferricyanide reductase from Ascaris muscle microsomes. 3 74

The lipid composition of yeast cells was manipulated by the use of an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae. There was a 2-3-fold decrease in the concentration of cytochromes a+a3 when the unsaturated fatty acid content of the cells was decreased from 60-70% of the total fatty acid to 20-30%. The amounts of cytochromes b and c were also decreased under these conditions, but to a lesser extent. Further lipid depletion, to proportions of less than 20% unsaturated fatty acid, led to a dramatic decrease in the content of all cytochromes, particularly cytochromes a+a3. The ATPase (adenosine triphosphatase), succinate oxidase and NADH oxidase activities of the isolated mitochondria also varied with the degree of unsaturation of the membrane lipids. The lower the percentage of unsaturated fatty acid, the lower was the enzymic activity. Inhibition of mitochondrial ATPase by oligomycin, on the other hand, was not markedly influenced by the membrane-lipid unsaturation. Npn-linear Arrenius plots of mitochondrial membrane-bound enzymes showed transition temperatures that were dependent on the degree of membrane-lipid unsaturation. The greater the degree of lipid unsaturation, the lower was the transition temperature. It was concluded that the degree of unsaturation of the membrane lipids plays an important role in determining the properties of mitochondrial membrane-bound enzymes.
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PMID:Membrane-lipid unsaturation and mitochondrial function in Saacharomyces cerevisiae. 12 85

Measurement of certain membrane-bound enzymic activities was used to study the orientation of the outer membrane of the double-membraned forespore of Bacillus megaterium KM. 2. Adenosine triphosphatase, NADH dehydrogenase and L-malate intact protoplasts, but were readily detected in intact stage II or IV forespores, consistent with reversed polarity of the outer forespore membrane relative to the mother-cell plasma membrane. 3. Measurement of NADH oxidase activity revealed that intact stage III forespores had the same high affinity for NADH as protoplast membrane preparations and protoplast lystates, consistent with ready access of NADH to oxidation sites on the outer forespores membrane. 4. Forespores and protoplasts showed osmometric behaviour in solutions of non-permanent solutes consistent with the presence of an intact permeability barrier in these structures.
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PMID:Biochemical evidence for the reversed polarity of the outer membrane of the bacterial forespore. 13 69

The effects of the inhibitors dicyclohexyl-carbodiimide (DCCD), bathophenanthroline and tertiary octylcatechol, on some enzyme activities in membranes from strains of Escherichia coli carrying mutations in the uncB or uncC genes have been studied. Membranes prepared from uncC mutants retain a normal DCCD-sensitive Mg2+-stimulated adenosine triphosphatase (Mg-ATPase) activity whereas in uncB mutants this enzyme activity is insensitive to DCCD. The membrane-bound Mg-ATPase activity from the uncC mutant strain, as compared with that from the normal strain, is only partially sensitive to the inhibitors bathophenanthroline or tertiary-octylcatechol. Both of these inhibitors stimulate the membrane-bound Mg-ATPase from uncB mutant strains. A DCCD-insensitive Mg-ATPase activity is found in the cytoplasmic fraction following cell disruption of either the uncB or the uncC mutants. The lipophilic chelators bathophenanthroline and tertiary-octylcatechol stimulate the activity of the 'soluble' Mg-ATPase in the uncB mutant but partially inhibit the activity in the uncC mutant. The NADH oxidase activities in membranes from both mutant and normal strains are strongly inhibited by tertiary-octylcatechol and bathophenanthroline but not by DCCD.
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PMID:Different effects of inhibitors on two mutants of Escherichia coli K12 affected in the Fo portion of the adenosine triphosphatase complex. 14 61

Two membrane-bound enzymes were localized by electron microscope cytochemical techniques in Plasmodium lophurae and its host erythrocyte. Parasites were prepared by saponin lysis, French pressure cell lysis, or anti-red blood cell serum lysis; infected and uninfected erythrocyte ghosts were prepared by saponin or French pressure cell lysis. Enzyme incubations were performed on unfixed cells. Adenosinetriphosphatase (EC 3.6.1.3) activity was found on the inside of the ghost membrane and on the inside of the outer parasite membrane. NADH oxidase was found on the outside of the erythrocyte membrane and on the outside of the parasite outer membrane. The parasite plasma membrane was negative for both enzymes. The location of both enzymes on the outer parasite membrane were reversed from what one would have expected if the outer membrane had remained merely an invaginated erythrocyte membrane. It is concluded that the outer membrane, although derived from the red cell membrane, has been altered by its association with the malarial parasite.
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PMID:Electron microscope cytochemistry of host-parasite membrane interactions in malaria. 14 26


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