bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interactions entre pigments et acides nucléiques
Authors: Ohba Y. , Fromageot P. 
Published: March 2005

Luteoskyrine, a bis‐polyhydroxyanthraquinone, is a toxic pigment produced by Penicillium islandicum. Its ingestion results in hepatomas and cirrhotic degeneration of the liver in man and the rat. This pigment is able to form in vitro and in the presence of Mg2+ ions two types of complexes with DNA. The first (I) and rapidly formed complex corresponds to an interaction with the purines of the DNA. To react luteoskyrine with the DNA purines, the DNA must be denatured. The interaction is established by the following criteria:

In the presence of denatured DNA the insoluble luteoskyrine‐Mg2+ complex is not formed.
The spectrum of luteoskyrine in aqueous solution is shifted to shorter wave lengths.
When submitted to ultracentrifugation and analysed at 260 mμ, and at 450 mμ the denatured DNA and the luteoskyrine sediment at the same rate, and the sedimentation coefficient of the complex is greater than that of the same sample of DNA alone.
After addition of luteoskyrine and magnesium ions, partially structured DNA is stabilized against further heat denaturation. Similar complexes (type I) are also formed with poly A, poly G and poly I. In each case, the spectra obtained and their stability are characteristic of the polymer utilised. Therefore the complexes of type I are said to be specific.

The second type of complex, type (II), on the contrary, is made slowly with native DNA or paired ribopolymers (poly A:U or poly G:C) irrespective of the nature of the constituent bases. Type II complexes can also be slowly formed from the type I complexes first made with denatured DNA. The spectra of the type II complexes are not characteristic of the nucleic acids involved but are very similar to those corresponding to the aggregated luteoskyrine‐Mg2+ complex.
Sheep Kidney Nuclease
Authors: Kasai K. , Grunberg‐Manago M. 
Published: March 2005

An endonuclease showing no apparent base specificity, nor any preference for the sugar moiety has been isolated from sheep kidney. The products of the digestion are 5′‐P‐ended oligonucleotides, and not mononucleotides. Preparation of short oligo A and oligo U (di‐, tri‐, tetra‐) with a good yield is described. The enzyme requires Mg ions, is inhibited at high ionic strength and destroyed by temperatures of 60° and above.The enzyme displays an extremely rigorous specificity with regard to the secondary structure of its substrate. This structural specificity is apparent from the fact that native DNA, complexes between poly A and poly U, and polyinosinic acid in high salt are completely resistant to the enzyme. Even poly A and poly C, at neutral pH denatured DNA, ribosomal RNA, and especially tRNA, are only slowly attacked.Preliminary experiments on the effect of addition of poly U on the hydrolysis of a copolymer A, C suggest that the enzyme will hydrolyze the unstructured loop of polyribonucleotide complexes.The analysis of the hydrolysis of tRNAs by sheep kidney unclease shows that the enzyme attacks all chains and produces mainly large fragments (average chain length, 40 nucleotide units), containing pGp terminal and TpΨpCpG sequences; and small oligonucleotides (average chain length 4.5 nucleotide units), containing a large amount of fragments with a CpCpA terminal.These results are discussed in relation to the conformation of tRNA.
Préparation de RNA Messager de Réticulocytes de Lapin par Ultracentrifugation en Rotor Zonal
Authors: Huez G. , Burny A. , Marbaix G. , Schram E. 
Published: March 2005

Two methods are described for the rapid isolation of 0.6 mg to 1 mg of 9S RNA from rabbit reticulocytes. This RNA has properties expected for messenger RNA.In the first procedure, reticulocyte polyribosomes are dissolved in 0.5% (w/v) sodium dodecylsulfate and messenger RNA is separated by sucrose gradient centrifugation in a zonal rotor (B IV‐Spinco).In the second method, messenger RNA is detached from polyribosomes by EDTA (3x10−2M) treatment and separated from ribosomal sub‐particles by sucrose gradient centrifugation using the same rotor.In both cases, messenger RNA is then concentrated by adsorption on a non‐ionic cellulose column.Further purification may be obtained by sucrose gradient centrifugations using the rotor S. W. 25.2 (Spinco).
The Localization and Function of Carnitine Acetyltransferase in the Flight Muscles of the Locust
Authors: Beenakkers A. M. T. , Henderson P. T. 
Published: March 2005

In order to determine the extent to which carnitine acetyltransferase is restricted to mitochondria, its occurrence in fractions of the flight muscles of Locusta migratoria, obtained by two different procedures, was checked by simultaneous assay of known mitochondrial enzymes.In one procedure, fractionated extraction of the muscles was achieved by gently stirring the tissue successively in isotonic sucrose and phosphate buffer after which the residue was disrupted in phosphate buffer. In the second procedure fractionation was achieved by differential centrifugation.In both procedures the partitioning of the carnitine acetyltransferase among all fractions closely paralleled that of the intramitochondrial marker enzymes, thus strongly suggesting that carnitine acetyltransferase is exclusively localized within mitochondria–possibly with the transferase occurring in two intramitochondrial compartments separated from each other by a mimbrane which is impermeable to acetyl CoA.The last‐named hypothesis is furthermore supported by correlated studies on mitochondrial respiration using acetate derivatives as substrates.
The Response of the Respiratory Chain and Adenine Nucleotide System to Oxidative Phosphorylation in Yeast Mitochondria
Authors: Onishi T. , Kröger A. , Heldt H. W. , Pfaff E. , Klingenberg M. 
Published: March 2005

Properties and functions of the respiratory chain and of the nucleotide system were studied in mitochondria from Saccharomyces carlsbergensis and compared with those in mitochondria from mammalian tissues.The composition of the respiratory chain showed a comparatively high content of DPN, ubiquinone, and cytochrome c.The failure of DPN to become reduced in the controlled state with any substrate confirms the absence of the first phosphorylation site. The redox states of the other components are controlled by the last two phosphorylation sites as in mammalian mitochondria.Substrates such as lactate, which feed hydrogen into the chain via cytochrome c, reduce ubiquinone in an energy‐dependent reverse electron transport.The mitochondrial content of nucleotides and of the 32P incorporating components was analysed. The mitochondria were found to have a similar equipment of nucleotides etc. as mammalian mitochondria.The phosphate transfer system in mitochondria was investigated. The phosphorylation rate of exogenous ADP is even at lower temperatures greater than that of endogenous ADP, in contrast to mammalian mitochondria.A specific exchange between exogenous and endogenous adenine nucleotides is found with similar properties as the exchange in mammalian mitochondria.
Dye‐sensitized Photooxidation as a Tool for the Elucidation of Critical Amino Acid Residues in Phosphoglucose Isomerase
Authors: Chatterjee G. C. , Noltmann E. A. 
Published: March 2005

Rabbit muscle phosphoglucose isomerase was subjected to methylene blue and rose bengal sensitized photooxidation. This treatment caused the enzyme to lose activity quite rapidly with half‐lives of 2 to 10 minutes under the following conditions: pH 7.1; ionie strength, 0.11; temperature, 10°; enzyme concentration, 2 mg per ml. The time progress curve for inactivation was of apparent first order only until approximately 50% of the initial enzyme activity were lost. Quantitative rate studies were therefore restricted to a comparison of rates obtained during this initial period of the inactivation process. The thus obtained pseudo‐first rate constants for inactivation were dependent on reaction volume, enzyme concentration, pH, and ionic strenth.The loss in enzyme activity was accompanied by an initial decrease in the histidine, cysteine, and methionine content followed, after more prologned oxidation, by a decrease also in tryptophan and tyrosine. Other amino acid residues were not affected, as determined by monitoring the change in total amino acid composition simultaneously with the loss in enzyme activiy as a function of the photooxidation time.A direct correlation between the rate of activity loss and the oxidation rate of a specific amino acid residue could not be established because of the multiplicity of the photocatalytic modifications. Kinetic studies of the photoinactivation process, however, implicate histidine as the residue whose modification is primarily involved in the loss of catalytic activity. A direct participation of methionine is considered unlikely on the basis of the ionic strength dependency of photoinactivation, while cysteine has been excluded on the basis of other studies with organic mercurials.
4‐Amino‐4,6‐Dideoxyhexoses Isolated from Lipopolysaccharides of Escherichia coli
Authors: Jann B. , Jann K. 
Published: March 2005

From the lipopolysaccharides of two Escherichia coli strains (serotypes O 7:K1:(L):H− and O10:K5 (L):H4) two unusual amino sugars were isolated.By sequential oxidation with periodate and hypoiodite, followed by identification of the reaction products, the aminosugars were characterized as 4‐amino‐4,6‐dideoxy‐d‐hexoses.The chromatographic properties of the amino sugars and their N‐acetyl derivatives were compared with those of authentic samples of free and N‐acetylated 4‐amino‐4,6‐dideoxy‐d‐glucose and 4‐amino‐4,6‐dideoxy‐d‐galactose. On the basis of the results obtained the unknown amino sugars were tentatively identified as 4‐amino‐4,6‐dideoxy‐d‐glucose (from the lipopoly‐saccharide of E. coli O7:K1:(L):H−) and 4‐amino‐4,6‐dideoxy‐d‐galactose (from the lipopolysaccharide of E. coli O10:K5(L):H4).This is the first time that 4‐amino‐4,6‐dideoxy‐d‐galactose is described as a constituent of a polysaccharide.
Zur Regulation der Synthese der Malatdehydrogenasen aus Cytosol und Mitochondrien von Rattenleber
Authors: Berkeš‐Tomaševi P. , Holzer H. 
Published: March 2005

Nuclei, mitochondria, microsomes and cytosol were obtained from rat liver homogenates in sucrose solution by centrifugal fractionation. Dise electrophoresis exhibits the existence of two separately migrating malate dehydrogenases in these particulate fractions. One of them is preferably found in the mitochondria, the other one in the cytosol. The two malate dehydrogenase separated by disc electrophoresis are probably identical with the mitochondrial and cytoplasmic malate dehydrogenases differentiated earlier by other authors observing their different reaction kinetics with oxaloacetate.In starvation the malate dehydrogenase activity in the cytoplasm decreased, whereas that in the mitochondria increased. The increase in mitochondrial activity is prevented by actinomycin. The decrease of cytoplasmic malate dehydrogenase caused by starvation is aggravated by actinomycin. All these effects are similar if the malate dehydrogenase activities are expressed as units per g liver fresh weight, per g body weight or per mg protein content in the extract.The regulation of malate dehydrogenase in the mitochondria is discussed as repression by carbohydrates (or a metabolite originating from carbohydrates). The increase of the enzyme in starvation can therefore be understood as “derepression.” As was found by other authors [2, 16, 17a], mitochondrial malate dehydrogenase participates in gluconeogenesis in the liver; thus a repression of this enzyme by carbohydrates appears “useful for the cell economy”. Probably only the fraction of malate dehydrogenase activity additionally arising in starvation is necessary for gluconeogenesis, whereas the mitochondrial malate dehydrogenase present in normal nutrition is functioning for carbohydrate catabolism in the citric acid cycle.
Reinigung und Charakterisierung der durch Östrogene induzierbaren 17‐β‐Hydroxysteroid: NAD(P)‐Oxydoreduktase aus dem Myometrium von Kaninchen
Authors: Jütting G. , Thun K. J. , Kuss E. 
Published: March 2005

The myometrium of the rabbit contains a 17‐β‐hydroxysteroid: NAD(P) oxidoreductase, whose specific activity depends on the functional state of the uterus. In pregnancy one observes a 25‐fold increase and after parenteral administration of oestradiol or stilboestrol an approximately 50‐fold increase compared to the normal adult rabbit.The enzyme was purified from myometrium about 100‐fold by precipitation twice with ammonium sulfate and by gel filtration.The enzyme was assayed by incubation with [16‐14C]oestradiol‐17β, determining oestron as the reaction product. Specific activity was expressed as n‐moles oestron/60 min/mg protein. The molecular weight of the 17‐β‐hydroxysteroid: NAD(P) oxidoreductase can be estimated from gel filtration studies in the range from 10,000 to 50,000.The enzyme requires NAD+ or NADP+ as cofactor, NADP+ giving a 20% lower activity than an equimolar amount of NAD+. The optimal pH for the enzymatic oxidation of oestradiol to oestron is 9.4, and for the reduction of oestron to oestradiol 6.4. The Michaelis‐Menten constant for oestradiol is 7.6 × 10−6 M. The oxidation of testosterone is at least 100 times slower than that of oestradiol. In phosphate‐free buffer solutions, the addition of phosphate gives an increase of the enzyme activity. p‐Chlormercuribenzoic acid (10−4M) and o‐iodosobenzoic acid (10−4M) inhibit the activity of 17‐β‐hydroxysteroid: NAD(P)oxidoreductase of the myometrium by 97% and 26% respectively.
Relation of Properties of Isolated Myosin to those of Intact Muscles of the Cat and Sloth
Authors: Bárány M. , Conover T. E. , Schliselfeld L. H. , Gaetjens E. , Goffart M. 
Published: March 2005

Myosin was prepared from the extensor digitorum longus, gastrocnemius medialis and lateralis, tibialis anterior, flexor of the claws of the anterior limb, and diaphragm muscles of the cat and didactyl sloth (Choloepus hoffmanni Peters). Actin‐activated, Ca2+‐activated, and EDTA‐activated ATPase activities of the myosins from cat muscles were two to four times higher than those of the myosins from the same muscles of the sloth. The difference in the Ca2+‐activated ATPase activity was found in the pH range of 5.5 to 10.0, and in the KCl concentration range of 50 mM to 500 mM at pH 7.0.The kinetic characteristics of the two myosins indicated that both the Km and the Vmax of the ATPase activities of the sloth myosin were lower than those of cat myosin by a factor of several‐fold.Reconstituted cat actomyosin superprecipitated four to six times faster than sloth actomyosin. This difference in the superprecipitation did not vary appreciably when the concentration of ATP and the ratio of myosin to actin were varied. A correlation between the ATPase activity and the speed of superprecipitation of actomyosins of the cat and sloth was shown.The contraction time of various muscles of the cat and sloth was found to be inversely proportional to the actin‐activated ATPase activity of their respective myosins. The speed constant of shortening of the muscles of the diaphragm appeared to be proportional to the actin‐activated ATPase activity of their myosin.In contrast to the ATPase activity of myosin, which varied according to the speed of contraction, the actin‐binding ability of myosins of the cat and sloth was rather constant. The extent of superprecipitation of various reconstituted actomyosins of the cat and sloth was also the same. These properties of the isolated myosins were related to the similar tension output of the muscles of the cat and sloth.
Studies on Mutant Phenylalanyl RNA Synthetases of Escherichia coli
Authors: Böck A. 
Published: March 2005

The temperature conditional mutant NP 37 of Escherichia coli differs from the wild type K 10 in that cell‐free extracts exhibit a 20‐fold reduced specific activity of phenylalanyl RNA synthetase. The mutant enzyme activity is characterized by an increased Km value for phenylalanine. Molecular weight determinations by sucrose density gradient centrifugation yield an approximate value of 180,000 for the wild type enzyme and of 100–110,000 for that of the mutant. Immunological analysis of the mutant extracts in these experiments, by means of antiserum prepared against purified phenylalanyl RNA synthetase, shows no cross‐reacting material at the position where the native enzyme sediments. However, an increased amount of cross‐reacting material is present in the fractions containing the mutant enzyme activity.A phenotypic revertant of NP 37 was found to possess heat stability properties of the phenylalanyl RNA synthetase intermediate between the wild type and the NP 37 enzymes. Incubation of cell‐free extracts of such a results in preparations which show the catalytic properties of phenylalanyl RNA synthetase that are characteristic of mutant NP 37.The results indicate that temperature inactivation of phenylalanyl RNA synthetase in NP 37 is a consequence of the dissociation of the enzyme into subunits with impaired catalytic properties.
Kupplungsreaktion an Lactatdehydrogenase nach reversibler Maskierung der SH‐Gruppen
Authors: Pfleiderer G. , Jeckel D. 
Published: March 2005

For some time there have been indications of the importance of histidine and tyrosine for the catalytic activity of lactate dehydrogenase. The presence of reactive sulfhydryl groups in this enzyme has made it difficult to modify the histidine and tyrosine groups chemically without destroying the SH‐groups at the same time. We have thus attempted to mask all the sulfhydryl groups reversibly so that the reaction of diazotised [35S]sulfanilic acid with the protein could be examined.The essential SH‐groups of the protein could be protected by adding a small excess of p‐chloromercuribenzoate or by forming a mixed disulphide with 5,5′‐dithiobis‐(2‐nitrobenzoic acid). The organo‐mercury derivative of lactate dehydrogenase, which had a residual activity of 13%, recovered 60% of the original enzymic activity on standing in pyrophosphate buffer, pH 8.5. The enzyme could not be fully reactivated on adding glutathione. Under the same conditions, there was a slow liberation of 2‐nitro‐5‐mercaptobenzoate from the enzyme which had reacted with 5,5′‐dithiobis‐(2‐nitrobenzoic acid). Coupling these modified lactate dehydrogenase preparations resulted in a fall in the SH‐titre of the enzyme. An attempt was thus made to mask all the sulfhydryl groups of the enzyme reversibly by means of the above mentioned reagents. When more than 1.5 g molecules of SH‐groups/36,000 g protein had reacted it was no longer possible to achieve 100% reactivation with cysteine.In a final attempt, the complex of lactate dehydrogenase with mercuric chloride was prepared. This derivative was inactive and contained no free thiol groups. Both the original enzymic activity and SH‐titre were fully restored with cysteine. Like the native enzyme, Hg‐lactate dehydrogenase also binds 4 molecules of the NAD‐sulphite complex, albeit with an increased dissociation constant.Hg‐lactate dehydrogenase was coupled with diazotised [35S]sulfanilic acid. The reaction was stopped with resorcinol and the reaction mixture was treated with cysteine. By this procedure the enzyme could be inhibited without loss of SH‐groups. The specific enzymic activity of the inhibited enzyme was proportional to the incorporation of 35S up to a value of 1.5 azoresidues/subunit. Azo‐lactate dehydrogenase migrated to the anode more rapidly than the native enzyme during electrophoresis at pH 8.5.
On the Mechanisms of Photochemical Reductions of FAD and FAD‐Dependent Flavoproteins
Authors: McCormick D. B. , Koster J. F. , Veeger C. 
Published: March 2005

The rate for photoreduction of riboflavin 5′‐phosphate is faster than flavin‐adenine dinucleotide which can be effectively photoreduced to the hydroquinone level by: ethylenediaminetetraacetate > ethylenediaminetetrapropionate > l‐methionine > nicotine > dimethylamino‐propanol > dimethylglycine ethyl ester > triethylamine. The same compounds can be used to photoreduce flavoproteins, the rates for which are: d‐amino acid oxidase > l‐amino acid oxidase > glucose oxidase > oxynitrilase > Shethna flavoprotein. The oxidation, reduction stage achieved is characteristics of the protein.Addition of free flavin markedly enhances the photoreduction of those flavoproteins which have a readily dissociable flavin‐adenine dinucleotide. Urea enhances the photoreduction rate of flavoproteins in approximate corespondence to their ease of photoreduction in the absence of this reagent. Increase in temperature does not greatly enhance the rate of photoreduction of these flavoproteins. Benzoate decreases the rate of photoreduction of certain of the oxidases.
Studies on the Specificity of the Enzymic Synthesis of Polyribonucleotides
Authors: Farber F. E. , Chargaff E. 
Published: March 2005

The purpose of this study was to ascertain whether enzymes having the same function (in this case, polynucleotide phosphorylase), but isolated from two very distant cell types, differed in their synthetic capacities. The enzymes were isolated from B. cereus, an organism possessing a DNA of a marked AT‐type (dissymmetry ratio of 1.70), and from M. lysodeikticus, whose DNA is of a pronounced GC‐type (dissymmetry ratio, 0.39). The approximate molecular weight of the B. cereus enzyme was found to be 210,000.In both instances, and with several independent enzyme preparations from either source, the mixed polynucleotides synthesized from CDP and ADP as the precursors were investigated. Three conditions of the proportions of the precursor pool were imposed, with the input ratio of CDP/ADP as 2, 1 or 0.5.Several criteria were employed for the study and the comparison of the synthetic polymers. The analysis of the base composition showed that, under equal conditions, the M. lysodeikticus enzyme incorporated a considerably higher proportion of CDP into the polynucleotides than did the B. cereus enzyme. The existence of concrete differences between polynucleotides synthesized by the two enzymes was emphasized by the study of the distribution of oligonucleotide fragments produced by the action of ribonuclease.The statistical treatment of the frequency of adenylic acid runs of different length in the various polymers demonstrated that both enzymes produced heteropolymers composed of randomly arranged nucleotide sequences.It is suggested that polynucleotide phosphorylase is species‐specific with respect to discrimination between precursors, but unspecific in its mode of action: the incorporated nucleotides are aligned in a random arrangement.