bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comportement du N‐acétylphénylalanyl‐tRNA dans un système acellulaire de Mammifère permettant la synthèse de polyphénylalanine
Authors: Reboud J. P. 
Published: March 2005

The behavior of N‐acetylphenylalanyl‐tRNA as an initiator of phenylalanine polymerisation in an Escherichia coli cell‐free system shows some analogy with the behavior of formylmethionyl‐tRNA during the synthesis of natural proteins. At low Mg++ concentrations, polyphenylalanine chain initiation depends on N‐acetylphenylalanyl‐tRNA and the same initiation factors which are required for protein chain initiation with formylmethionyl‐tRNA.However in a rabbit reticulocyte cell‐free system, N‐acetylphenylalanine is not incorporated into polyphénylalanine at any Mg++ concentration. In this paper, we showed that:a) N‐acetylphenylalanyl‐tRNA did bind to reticulocyte ribosomes in the presence of poly U. This binding was GTP dependent and needed a factor which was extracted by washing ribosomes with salt (NH4Cl 1 M);b) the bound N‐acetylphenylalanyl‐tRNA was partially released by puromycin or by addition of phenylalanyl‐tRNA. In this last case, incorporation of N‐acetylphenylalanine into polyphenyl‐alanine was noticed (ratio N‐acetylphenylalanine/phenylalanine = 1/20);c) the ribosomal wash fluid also greatly enhanced phenylalanyl‐tRNA binding to salttreated ribosomes, in the presence of poly U and GTP. The maximum binding was obtained with the same concentrations of Mg++ and K+ as for N‐acetylphenylalanyl‐tRNA binding. It was not possible to separate on a DEAE‐cellulose column the factors that were required for phenylalanyl‐tRNA and acetylphenylalanyl‐tRNA binding. On the other hand, a preparation of the binding enzyme from reticulcyte supernatant enhanced both phenylalanyl‐tRNA and acetyl‐phenylalanyl‐tRNA binding to ribosomes;d) the optimum Mg++ concentration for phenylalanine polymerisation was higher with salt‐washed ribosomes than with sucrose‐washed ribosomes. Adding the wash fluid shifted the Mg++ optimum back to the lower value. N‐acetylphenylalanyl‐tRNA was not required for this shift as noticed in Escherichia coli.One likely explanation of our results with reticulocytes is the possibility that the “binding enzyme” of Schweet et al., which was present in our ribosome wash fluid, could work with both N‐acetyl as well as with phenylalanyl‐tRNA. Thus, the inability to incorporate N‐acetylphenyl‐alanine might be due to a competition between these two compounds for the same enzyme and the same ribosomal site. If this is indeed the case, it is in marked contrast to results obtained with Escherichia coli and could reflect a basic difference in the mechanism of protein chain initiation.
Enzymes Involved in Fructose Metabolism in Liver and the Glyceraldehyde Metabolic Crossroads
Authors: Sillero M. A. G. , Sillero A. , Sols A. 
Published: March 2005

Fructokinase, the B isoenzyme of fructosediphosphate aldolase and triokinase, the three enzymes of the Hers' pathway for fructose metabolism, are constitutive in adult rats.A quantitative model of the metabolic crossroads of d‐glyceraldehyde has been developed. This model permits a prediction of the relative contributions of the phosphorylative, oxidative and reductive pathways in different conditions. The main pathway for d‐glyceraldehyde metabolism in liver is phosphorylation by triokinase.
An Optical Rotatory Dispersion Investigation of Fungal Laccase
Authors: Bossa F. , Rotilio G. , Fasella P. , Malmström B. G. 
Published: March 2005

The optical rotatory dispersion curves for fungal laccase A and B have been determined in the wavelength region 200–750 nm.
Both proteins show pronounced Cotton effects in the visible region. These are discussed in terms of possible chromophores (the so‐called Type 1 and Type 2 Cu2+ as well as the two diamagnetic copper ions). Various chemical treatments indicate that the anomalous dispersion is mainly associated with the blue, Type 1 Cu2+, which is thus coordinated in an asymmetric manner, but a small contribution from the Type 2 Cu2+ cannot be excluded.
There are several Cotton effects in the ultraviolet region, probably associated with aromatic amino acids and peptide bonds in α‐helical configuration, but possible contributions from carbohydrates and disulfide bridges are also considered. The curves in the ultraviolet region do not change on complete reduction of the enzyme, indicating that there are no gross conformational changes on reduction and that the groups giving rise to the anomalous dispersion in this region are not associated with the electron‐accepting sites.
Suche nach einem Metaboliten bei Vergiftung mit Desmethylphalloin (DMP)
Authors: Puchinger H. , Wieland Th. 
Published: March 2005

Various observations cited at the beginning of this paper and in the Discussion suggested that phalloidine, a poisonous constituent of the green mushroom Amanita phalloides, would not be toxic by itself, but would be rendered toxic previously in the liver. Using a tritiated toxic derivative of phalloidine ([3H]desmethylphalloin) we found that:(a) in rats, 60% of the administered substance are excreted unchanged in the urine within the first day. A second radioactive substance of low concentration, moving more slowly in paper chromatography, turned out as a product of the self‐degradation of [3H]desmethylphalloin;(b) respectively 98% and 99,9% of the radioactivity were extracted with methanol from homogenates of livers of rats or mice which had received [3H]desmethylphalloin 1 to 2 hours before. Aqueous homogenates of liver of poisened rats also contained radioactivity firmly bound to a high molecular weight substance, as shown by gel chromatography. The radioactive substance was totally removed from the carrier, presumably ribosomal material, by adding methanol, and was identified as [3H]desmethylphalloin;(c) [3H]desmethylphalloin was not metabolized on incubation with oxygen and rat liver ribosomes in a NADPH‐regenerating system. A radioactive substance extracted from liver microsomes of a poisoned rat also proved to be original toxin.As a result of these experiments it can be concluded that [3H]desmethylphalloin and most probably also phalloidine are not metabolized in the livers of rats and mice.
Glutamic‐Aspartic Transaminase — Antitransaminase Interaction:
Authors: Patramani I. , Katsiri K. , Pistevou E. , Kalogerakos T. , Pavlatos M. , Evangelopoulos A. E. 
Published: March 2005

Transaminase was cross‐linked with various proteins after the addition of glutaraldehyde or ethyl chloroformate. The water insoluble conjugates were used for the purification of antitransaminase and antiapotransaminase. A method is described.
Pig heart transaminase and ox heart transaminase react differently with anti‐pig‐heart transaminase and apotransaminase. Slight differences were also observed in the reactions between holoenzyme and apoenzyme with their homologous and heterologous antibodies.
l‐Aspartate and α‐ketoglutarate protect transaminase from the inhibitory action of antitransaminase. Pyridoxal‐5′‐phosphate has no effect on the enzyme‐antienzyme binding when added in the system in stoichiometric amounts. Higher concentrations of the coenzyme, however, activate the complex antigen‐antibody by facilitating its solubilization.
The intact conformation of transaminase is not essential for enzyme‐antienzyme‐binding. Peptides in the dialysate of a tryptic or a chymotryptic hydrolysate of transaminase were able to react with the antibody and form a precipitate.
Determination of Elastolytic Activity with 125I and 131I Labelled Elastin
Authors: Robert B. , Robert L. 
Published: March 2005

A method is described for the preparation of iodine labelled elastin of high specific activity using 131I or 125I. The labelled elastin is used as substrate for the study of the kinetics of elastolysis with crystalline elastase. Its high sensitivity renders the method suitable for the detection and determination of low levels of elastolytic activity. This method is compared to the one using azo‐dyed elastin (“azoelastin”). Similar kinetics, with a lag period are obtained with both methods. The enzyme concentration v. s. activity curve is a straight line with both methods up to a ratio of enzyme to substrate of 1:50 at least. The advantages of this method over the others proposed is its greater sensitivity and its safe use in colored and turbid media.This method was used for the detection of elastolytic activity in a number of animal, plant and fungal enzyme preparations. High activity was associated with pepsin, papaïn and pronase. Low, but distinct activity, was present in α‐chymotrypsin and ficin preparations. A purified bacterial collagenase had an intermediary activity. Crystalline trypsin had a very low, hardly detectable activity and plasmin had no activity.
Étude directe, par dialyse sur Sephadex G‐25, de la formation d'un complexe entre l'hexokinase de levure et ses substrats
Authors: Noat G. , Ricard J. , Borel M. , Got C. 
Published: March 2005

A hexokinase has been isolated from Baker's Yeast, purified and obtained in crystalline form. Its specific activity is between 600 and 700 units/mg. This enzyme is homogeneous on DEAE‐cellulose chromatography. The molecular weight, estimated by molecular sieving on Sephadex G‐100, is around 49000.The authors of the present article have been able to show, by equilibrium dialysis on Sephadex G‐25, that one molecule of the enzyme (MW 49000) binds one molecule of [14C]glucose in the absence of ATP. The value of the affinity constant for [14C]glucose, under the experimental conditions used and in the absence of ATP, is 10000 M–1. This value is nearly identical, within experimental errors, to 1/Km obtained from the measurement of hexokinase activity.The binding of the Mg[14C]ATP2– chelate on the enzyme cannot be detected in the absence of glucose and under the experimental conditions used. This result implies that the affinity constant of the hexokinase for MgATP2– is lower than 800 M–1. The value of 1/Km for the ATPase reaction, determined under the same experimental conditions, is around 200 M–1.These results are compatible with an ordered mechanism of hexokinase catalysis, in which the enzyme binds glucose first. They seem difficult to reconcile with a rapid equilibrium random mechanism.
Evidence for Two Molecular Forms of Streptococcal Erythrogenic Toxin
Authors: Nauciel C. , Blass J. , Mangalo R. , Raynaud M. 
Published: March 2005

Two molecular forms of streptococcal erythrogenic toxin have been isolated by DEAE‐cellulose chromatography.These two forms exhibit the same biological and immunological properties. They have the same sedimentation coefficient s20= 2.52. Molecular weight is about 30 000. The protein is made of a single polypeptide chain with glutamic acid as N‐terminal amino acid.Exposure to 2‐mercaptoethanol induces conversion to a single form.The possibility that the different molecular forms arise from the binding of small molecules of different charge through a sulfhydryl group of the protein is discussed.
Amino Acid Sequence of a 22‐Residue Section from the Variable Part of Pig Immunoglobulin λ‐Chains
Authors: Franěk F. , Keil B. , ŠOrm F. 
Published: March 2005

The section which represents a part of a larger fragment of the variable part of pig immunoglobulin λ‐chains is constituted by two peptides (18 residues and 4 residues) of variable character. These peptides were fractionated and their amino acid sequence determined. At certain positions two to four different amino acids were found. There is a close relation between the found amino acid sequenceAla‐Thr‐Leu‐Thr‐Ile‐Thr‐Gly‐Ala‐Gln‐Ala‐Glu‐Asp‐Glu‐Ala‐Asp‐Tyr‐Phe‐Cys‐Ala‐Leu‐Tyr‐LysAla Leu Ala Asn Ser Gly Arg Gly Gly Thr Gly and the amino acid sequence of the corresponding region of human type L Bence‐Jones proteins.
Über die Substrat‐ und Hormoninduktion der Tryptophan‐Oxygenase in der isoliert perfundierten Rattenleber
Authors: Staib R. , Thienhaus R. , Ammedick U. , Staib W. 
Published: March 2005

This paper deals with investigations in isolated perfused rat livers on tryptophan‐oxygenase activity under various experimental conditions. Enzyme‐activity showed a linear rise with rising amounts of tryptophan (0; 125 and 250 mg of tryptophan/kg) in the perfusate. Adrenalectomized and sham‐operated animals have been compared and activity in the adrenalectomized rats were significantly lower in all cases.A significant decrease in the substrate induced increase of tryptophan‐oxygenase‐activity occured 12 h after adrenalectomy. Substrate‐concentration was 250 mg/kg in these experiments.The influence of substrate and cortisol on tryptophan‐oxygenase‐activity has been investigated 7 days after operation. Combined application of both substrate and steroid resulted in no difference to sham‐operated animals when compared to substrate only in the same concentration. On the other hand, in livers from adrenalectomized rats values were significantly higher with combined application than in livers of adrenalectomized animals which received substrate only.The substrate‐dependent rise in tryptophan‐oxygenase‐activity could not be influenced by actinomycin D in contrast to the cortisol effect which was significantly inhibited under these conditions. Both “inducers” were inhibited by cycloheximid.These inhibition‐experiments suggest and confirm two different mechanisms of the substrate‐activation and steroid‐induction of tryptophan‐oxygenase.
Activité de treize enzymes du métabolisme intermédiaire, dans le foie du jeune rat qui récupère d'une malnutrition protidique
Authors: Camus J. , Vandermeers‐Piret M.‐C. , Wodon C. , Christophe J. 
Published: March 2005

100 g rats, submitted for 3 weeks to protein malnutrition (mostly lysine and threonine deficiency) with a diet offered ad libitum but containing 7% gluten as the sole protein, were starved for 24 h and allowed to recover for 3 days on a diet containing 18% casein and 0.3%dl‐methionine. These animals were compared to control rats refed on the gluten diet.The food intake as well as the level of immunoreactive plasma insulin increased immedieately. Among the free amino acids of the plasma, lysine, threonine and tyrosine rose rapidly (4‐ to 6‐fold), others were also significantly elevated while serine, glycine and histidine decreased.In the liver, the concentration of taurine was multiplied 7‐fold, that of threonine tripled, those of lysine, leucine, isoleucine, valine, tyrosine and phenylalanine doubled approximately, while the level of serine was markedly decreased. After 3 days, the total protein and DNA contents had increased by 70% and 2% respectively. Protein concentration on a wet weight basis was slightly higher than that observed in rats maintained on gluten whereas glycogen concentration levelled at a significantly lower (–43%) value. Of the 13 enzymatic specific activities investigated for their contribution to the intermediary metabolism, some did not vary significantly (α‐amylase bound to glycogen, hexokinases 1, 2 and 3, NADP:malate dehydrogenase, ATP:citrate lyase, arginase). Five activities increased (glucokinase 4‐fold, glucose‐6‐phosphate dehydrogenase 6‐fold, 6‐phosphogluconate dehydrogenase 2‐fold, serine dehydrogenase 2‐fold and ornithine aminotransferase 8‐fold) and three activities decreased somewhat (pyruvate kinases 0.60‐fold, glucose‐6‐phosphatase 0.65‐fold and fructose‐1,6‐diphosphatase 0.70‐fold).These rapid modifications might favour in the liver (a), a faster utilization of glucose in the two main glycolytic pathways; (b), a decrease in the hepatic glucose output and (c), the removal of the amino group of amino acids supplied in excess of the needs for protein storage.From these results and previously published experiments it thus appears that within the 3 days following a period of amino acid imbalance, insulin hypersecretion could not only have general effects on protein synthesis and turnover and on mitotic activity but might also be specifically involved in the induction of glucokinase and glucose‐6‐phosphate dehydrogenase and in the repression of glucose‐6‐phosphatase and fructose‐1,6‐diphosphatase. The influx of free amino acids plays the main role in the induction of serine dehydratase and ornithine aminotransferase and could share the responsability with insulin in the induction of glucokinase and glucose‐6‐phosphate dehydrogenase.
The Utilization of Exogenous Pyrimidines and the Recycling of Uridine‐5′‐Phosphate Derivatives in Saccharomyces cerevisiae, as Studied by Means of Mutants Affected in Pyrimidine Uptake and Metabolism
Authors: Grenson Marcelle 
Published: March 2005

Mutants impaired in cytosine uptake (cyt‐p) or in cytosine deamination (cyt‐da) are unable to use cytosine as a source of pyrimidines or as a source of nitrogen. The cyt‐p mutation makes it possible to define a specific cytosine permease.
A mutation (ura‐p) affecting exclusively uracil uptake delineates a specific uracil permease.
The study of mutants lacking uridine‐kinase activity (urid‐k) has shown that, whereas uridine can no longer be used as a source of pyrimidines in the absence of this enzymic activity, uridine kinase is not an obligatory step in the formation of UMP from uracil.
A mutation (urid‐p) affecting specifically uridine uptake delineates a uridine permease.
The behaviour of mutants (ups) blocked in UMP formation from uracil indicates that they have lost an enzyme catalyzing this reaction in one step.
A study of the mutants ups and urid‐k has shown that, when the utilization of uracil or uridine is decreased as a result of a mutation, the rate of uptake of uracil or uridine, respectively, is diminished by feedback inhibition of internal pyrimidines on the corresponding permeases, and, furthermore, that the enzymes coded or controlled by the ups and the urid‐k genes are not constituents of the transport systems.
The excretion of uracil by several mutants under different conditions has suggested that endogenous UMP liberates uracil in two steps catalyzed by a UMP phosphatase and a uridine‐ribohydrolase respectively. A mutant lacking the uridine‐ribohydrolase activity (urid‐rh) has been isolated. The observations reported suggest that uracil produced endogenously from UMP is continuously recycled.
The results of a chromatographic study of the fate of labelled pyrimidines added to the medium, and accumulated in the soluble pool, are in agreement with the interpretation of the various mutations.
The Antigenic Independence of the Three Aspartokinases of Escherichia coli K 12
Authors: Kaminski M. , Falcoz‐Kelly F. , Truffa‐Bachi P. , Patte J.‐C. , Cohen G. N. 
Published: March 2005

The immunological properties of three pure enzyme proteins carrying respectively the two threonine‐sensitive aspartokinase I and homoserine dehydrogenase I activities (Aspartokinase I—homoserine dehydrogenase I), the two methionine‐repressible aspartokinase II and homoserine dehydrogenase II activities (aspartokinase II—homoserine dehydrogenase II), and the lysine‐sensitive aspartokinase III (aspartokinase III), have been investigated by means of double diffusion precipitation in agar gel.The antigenic structures of these three proteins appeared different: no cross‐reactions were detected.
Metabolic Regulation of Polygalacturonic Acid trans‐Eliminase in Erwinia
Authors: Moran F. , Starr M. P. 
Published: March 2005

Strains of Erwinia carotovora and Erwinia aroideae, formerly thought only to be inducible, are constitutive for polygalacturonic acid trans‐eliminase. Maximum enzyme formation, however, occurs in the presence of polygalacturonic acid.
A release from strong catabolic repression enables glucose‐grown cultures to initiate their attack on polygalacturonic acid and, thereby, eliminates the necessity for the entry of the polymer into the cell.
A low constant proportion (less than 25%) of the total polygalacturonic acid trans‐eliminase is present in the culture fluid during the exponential growth‐phase of Erwinia carotovora. The enzyme may be regarded as an exoenzyme. The exact location of polygalacturonic acid trans‐eliminase in the cells was not established; it could be truly intracellular or reside between the cell‐wall and membrane.
Replication of Poliovirus RNA Studied by Gel Filtration and Electrophoresis
Authors: ÖBerg B. , Philipson L. 
Published: March 2005

The kinetics of synthesis of poliovirus RNA has been studied in suspension cultures of HeLa cells.Single stranded poliovirus RNA was separated from double stranded structures (replicative form and replicative intermediate) by gel filtration on sphere‐condensed agarose. Electrophoresis on polyacrylamide‐agarose gels was used for analytical separation of the three classes of poliovirus RNA in infected cells i. e. single stranded RNA, replicative form and replicative intermediate.Continuous labeling experiments confirmed that single stranded RNA is synthesized at a higher rate than the double stranded structures. Net synthesis of the replicative form levels off after 4 h of infection but the replicative form and the single stranded RNA are synthesized at high rates at later times. The replicative form probably precedes the single stranded RNA in the replication cycle.No free single strands complementary to viral RNA could be detected from 1 to 5 h after infection.Pulse labeling experiments reveal that the replicative form, the replicative intermediate and the single stranded RNA are synthesized at the highest rates 3–3.5 h post infection. The synthesis of the replicative intermediate and the single stranded RNA decreases at later times, while the replicative form synthesis continues unabated. At 3.5 h post infection a short (1 min) pulse introduces more label into the replicative intermediate than the single stranded RNA and the replicative form. As the length of the pulse increases the relative amount of label in the single stranded RNA increases, the replicative form remains constant and the replicative intermediate decreases. These results indicate a precursor‐product relationship between the replicative intermediate and the single stranded RNA, at 3.5 h post infection. At late times in the replication cycle most of the newly synthesized replicative form is not formed as an end product from the replicative intermediate.