bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Configurational Assay of Asymmetric Methyl Groups
Authors: Cornforth John W. , Redmond John W. , Eggerer Hermann , Buckel Wolfgang , Gutschow Christine 
Published: March 2005

By chemical synthesis starting from phenylacetylene and utilizing stereospecific reactions, two specimens of acetic acid were prepared in which the following conditions were closely approached: (a) some of the methyl groups consisted of one hydrogen, one deuterium, and one tritium atom attached to carbon; (b) all such methyl groups in one specimen had the R configuration, and all such methyl groups in the other specimen had the S configuration, and the correct absolute configuration was assignable to each specimen from the method of synthesis used; (c) all methyl groups containing a tritium atom also contained a deuterium atom.
Each specimen of acetic acid was converted enzymically into acetyl‐coenzyme A and (in the same incubation) this product was condensed with glyoxylic acid on malate synthase to form two specimens of S‐malic acid.
Each specimen of malic acid was incubated with fumarase until the tritium content of the organic acids (fumarate + malate) had ceased to fall.
Malic acid synthesized from R‐acetic acid retained 69% of its carbon‐bound tritium (in fumarate + malate) on incubation with fumarase. Malic acid synthesised from S‐acetic acid retained 31% of its carbon‐bound tritium.
The enzymic assay described in paragraphs 2–4 constitutes a method for determining the absolute configuration of asymmetric methyl groups, provided that a substantial proportion of the tritium in the specimen examined is present in such groups.
The method thus established can be used to study the mechanism of enzymic reactions in which a methylene group is converted stereospecifically into a methyl group. With one logical proviso–that it is necessary to known whether protium or deuterium is preferentially removed by the enzyme from methyl groups also containing tritium–the method is also applicable to enzymic reactions in which a methyl group is converted stereospecifically into a methylene group.
Subject to the above proviso, it is indicated that on malate synthase the removal of hydrogen and the attachment of the glyoxylate residue occurs with inversion of configuration.
Complexes of Liver Alcohol Dehydrogenase
Authors: Reynolds C. H. , Morris D. L. , Mckinley‐Mckee J. S. 
Published: March 2005

The Michaelis‐Menten‐type kinetics of inactivation of horse‐liver alcohol dehydrogenase with iodoacetate have been used to study the binding of a number of known ligands. Adenine nucleotides protect competitively with iodoacetate as do halides and aromatic acids. Uncharged chelating‐agents (orthophenanthroline, and 2,2′‐bipyridyl) protect non‐competitively. Uncharged monodentate ligands (e. g. imidazole) stimulate inactivation.The effect of imidazole on the binding of various ligands at pH 7.4 and at pH 10 was studied. Multiple inhibition analysis was used to examine the mutual interaction of pairs of substances which protected the enzyme from iodoacetate. ADP‐ribose and decanoate were mutually competitive, while AMP and orthophenanthroline were non‐competitive. Increasing the ionic strength was found to affect differently the mutual interactions of pairs of anions, as well as to weaken their binding to the enzyme.In some cases, kinetic studies of reduction of NAD+ were used to complement the inactivation studies.It is concluded that, in the coenzyme, the phosphate group nearer to adenosine is important for binding. Most, but not all, of the ligand‐ligand interactions can be explained by steric or electrostatic effects; it is tentatively suggested that conformational changes may also be involved. Precise interpretation, however, is complicated: there are two different types of zine in the enzyme, and anions might bind to either, or neither.
Isolation and Characterisation of the Peptides Derived from the α1‐Chain of Calf Skin Collagen after Hydroxylamine Cleavage
Authors: Heidemann E. , Heinrich W. 
Published: March 2005

The α1‐chain of acid soluble calf skin collagen was cleaved with hydroxylamine and the resulting peptides were separated and purified by ion exchange and molecular sieve chromatography.Four fragments were isolated, representing molecular weights of 20 000, 31 000, 45 000, and 48 000; also intact or probably slightly modified α1‐chains could be found. The peptides were renatured and precipitated as long spacing segment fragments using ATP; their order in the intact molecule was determined, using the electron microscopy, by their cross‐striation patterns.The different fragments are derived from the B‐end of the α1‐chain, only the shortest peptide derives from a middle region of the molecule. The content of the hydroxamic acids of the fragments varies from 0.59 to 1.18, the modified α1‐chain shows 2 groups of hydroxamic acid.In four of the five isolated fractions glycine could be determined as N‐terminal.
The Effect of Triton X‐100 on the Respiratory Chain Enzymes of a Heart‐Muscle Preparation
Authors: Soltysiak Dorota , Kaniuga Zbigniew 
Published: March 2005

The effect of non‐ionic detergent Triton X‐100 on the respiratory chain enzymes of a heartmuscle preparation was compared with that of deoxycholate.
The efficiency of the action of the detergents on the activity of membrane‐bound enzyme depends on both the detergent/protein ratio and the concentration of protein in the reaction mixture.
No essential differences both in the site and the degree of inhibition or activation of enzymic activities were observed due to the action of Triton X‐100 or deoxycholate when a suitable detergent/protein ratio was applied.
The usefulnes of non‐ionic detergent Triton X‐100 for the studies on several membrane‐bound enzymes is discussed.
Characterization of Neurospora crassa Mitochondria Prepared with a Grind‐Mill
Authors: Weiss Hanns , von Jagow Gebhard , Klingenberg Martin , Bücher Theodor 
Published: March 2005

Mitochondria can be isolated rapidly from Neurospora crassa with high yields by disrupting the hyphae suspension between the two grinding wheels of a simple mill.The isolated mitochondria respire with pyruvate + malate, succinate, and with NADH and NADPH in high rates and well coupled to oxidative phosphorylation.Three phosphorylation steps are involved in the oxidation of pyruvate and two in the oxidation of succinate, NADH and NADPH.Rotenone, antimycin and KCN inhibit the electron flow at the known steps.The cytochrome composition pattern is characterized by a particularly high content of cytochrome c.Evidence is given for the existence of two NADH‐dehydrogenases for the oxidation of exogenous and endogenous NADH with different localizations on the inner mitochondrial membrane.On the basis of these properties, mitochondria from Neurospora crassa can be looked upon in analogy to mitochondria from yeast, particularly from Torulopsis utilis.
Structure primaire de la caséine αS1 bovine
Authors: Grosclaude François , Mercier Jean‐Claude , Ribadeau‐Dumas Bruno 
Published: March 2005

This paper is the first one of a series devoted to the primary structure of the major protein of cow's milk, αS1‐casein, a single‐chain phosphoprotein, formerly reported to have arginine as an NH2‐terminal, and Leu‐TrpOH as COOH‐terminal residues.Tryptic digestion of maleyl αS1‐casein (genetic variant B), in theory limited to arginyl bonds, yields eight peptidic fragments, Tm 1 to Tm8, which were fractionated by column chromatography and, in some cases, more thoroughly purified by preparative paper electrophoresis and/or chromatography. The amino acid composition and the phosphate content of these fragments were determined.The fragments Tm3 and Tm8 arise from a partial non specific cleavage of Tm5. thus, six fragments only–Tm1,2,4,5,6 and 7–arise from the specific cleavage of the αS1‐casein chain at arginyl bonds, a result in accordance with the reported number of six arginyl residues in the chain, one being NH2‐terminal. The fragment Tm7, with two arginyl residues, and Tm2 devoid of arginine appear to represent respectively the NH2‐ and COOH‐terminal parts of the αS1‐casein chain.These peptidic fragments–except Tm4 which is devoid of lysine–were further digested by trypsin at lysyl bonds, after eliminating the blocking maleyl groups. The resulting peptides were purified by the same methods as mentioned above, and the composition of these tryptic peptides was established.As a control, the tryptic peptides of αS1‐casein were simultaneously purified by the same methods from a hydrolysate of the protein which had not been treated with maleic anhydride.In summary, this first step of our work gives: (a) the composition of all the bovine αS1‐casein tryptic peptides; (b) partial information on the location of these peptides in the protein chain; (c) confirmation that the molecular weight of the bovine αS1‐casein monomer is approximately 23 600.
Structure primaire de la caséine αS1 bovine
Authors: Mercier Jean‐Claude , Grosclaude François , Ribadeau‐Dumas Bruno 
Published: March 2005

A previous paper described the amino acid composition of the fragments resulting from selective cleavage of the bovine αS1‐casein polypeptide chain at arginyl bonds after blocking the lysyl residues by maleic anhydride.The fragment Tm2, which is 48 residues long, represents the COOH‐terminal part of the αS1‐casein chain, according to the following observations: (a) it is devoid of arginine; (b) only the peptide Tm2 is coloured by the Ehrlich reagent specific for Tryptophane; (c) the two amino acids released by carboxypeptidase A (successively Tryptophane and Leucine) are those of the COOH‐terminal end of αS1‐casein.The complete sequence of this large COOH‐terminal peptide obtained from αS1‐casein C was determined by classical methods, using endopeptidases to produce smaller peptides, then exopeptidases and the Edman sequential degradation procedure for establishing the amino acid sequence of these peptides.A part of this work has been published in a previous communication reporting the location, at the eighth position from the COOH‐terminal end, of the substitution Gly/Glu between the genetic variants αS1C and αS1B.
The Effects of Polyhydric and Monohydric Alcohols on the Heat Induced Reversible Denaturation of Chymotrypsinogen A
Authors: Gerlsma Sicco Y. 
Published: March 2005

The reversible thermal denaturation of chymotrypsinogen A was investigated in aqueous solutions of mono‐, di‐ and polyvalent alcohols.Sorbitol and erythritol show a stabilizing effect, whereas the di‐ and monovalent alcohols are destabilizing. Divalent alcohols have a less destabilizing influence than monovalent alcohols when equimolecular proportions of ‐CH2‐ and / or –CH3 groups are present.Stabilizing effects of the polyalchols can be explained in terms of a lessened H bond rupturing capacity of the medium.The destabilizing by di‐ and movovalent alcohols is attributed to their hydrophobic interaction with the protein, which increases with the number of ‐CH2‐ and, or ‐CH3 groups and decreases with the number of ‐OH groups.Chymotrypsinogen A is more destabilized by hydrophobic alcohols than ribonuclease.
Regulation of Histidine Uptake by Specific Feedback Inhibition of Two Histidine Permeases in Saccharomyces cerevisiae
Authors: Crabeel Marjolaine , Grenson Marcelle 
Published: March 2005

Although a large fraction of the histidine accumulated from the medium remains free and intact in Saccharomyces cerevisiae, it is not exchangeable with external histidine. Hence, the steady state concentration level of histidine is not determined by a balance between rates of inflow and outflow.Preloading the cells with histidine results in a rapid inhibition of histidine uptake, whereas preloading with other amino acids has no effect on histidine uptake.The inhibition by internal histidine affects the activity, and not the synthesis, of two specific histidine permeases. The histidine permease with high affinity for histidine is much more sensitive to this inhibition than the second histidine permease.A mutant (his‐p1) specifically affected in histidine uptake was isolated.Criteria for demonstrating that a mutation or a feedback control directly affect an uptake system are discussed.It is concluded that the his‐p1 mutant is histidine‐permease‐less, and that the activity of the histidine permeases are regulated by specific feedback inhibition.
Solubilisation de l'acétylcholinestérase des organes électriques de gymnote
Authors: Massoulié Jean , Rieger François , Tsuji Shigeru 
Published: March 2005

Further evidence is presented in this paper concerning the occurence of three different molecular species of acetylcholinesterase in the electric eel's electric organ. These species, A, C, and D, differ in their sedimentation coefficients (8.5 S, 14.2 S, and 18.4 S, respectively). We show that the whole of the tissue acetylcholinesterase activity can be solubilized by repeated homogenisation, in the form of A, C, and D.Homogenisations under different conditions of ionic strength, or after prolonged autolysis yield closely similar results: the ratios of A, C, and D are remarkably constant. Moreover ammonium sulfate precipitation does not affect these species. This raises the question of their relationship and significance. All three species are recognized by antibodies obtained from rabbit immunized against the purified enzyme.We have also studied the solubilization of acetylcholinesterase by trypsin in electric tissue slices. This is very effective and directly yields species B. This species, which is homogeneous in sedimentation, but might contain a variety of slightly different protein molecules, can also be obtained by partial tryptic digestion of A, C, and D. The sedimentation coefficient of species B is very close to that of purified acetylcholinesterase and we have previously suggested that the two kinds of molecules may be similar. Even though this is probably correct, we have been able to detect a significant difference (0.8 S unit) in the sedimentation coefficients.
Regulation of the Enzymes of the β‐Ketoadipate Pathway in Moraxella
Authors: Tresguerres M. Elena F. , DE Torrontegui Gertrudis , Ccánovas José L. , Ingledew W. Michael 
Published: March 2005

The ability to oxidize quinate is elicited in Acinetobacter calco‐aceticus not only by growth on quinate but also by growth on protocatechuate or its precursors such as shikimate and p‐hydroxybenzoate. Accordingly the synthesis of a quinate dependent dehydrogenase was found to be induced by protocatechuate. Moreover, this enzyme seems to belong to the same coordinate block of enzymes responsible for the conversion of shikimate to β‐ketoadipyl‐CoA.
Analogies between quinate and shikimate oxidation in A. calco‐aceticus have been substantiated by showing that both quinate dehydrogenase and shikimate dehydrogenase activities rely on a single enzyme.
Several auxotrophs that have lost the ability to utilize both quinate and shikimate as sole source of carbon and energy have been isolated. Particularly relevant for this study are two of these mutants in which the dehydrogenase is severely impaired and correspondingly their ability to oxidize the mentioned hydroaromatic compounds is substantially reduced. The properties of these auxotrophs and their revertants confirm the key role of the dehydrogenase in the dissimilation of both quinate and shikimate. The rationale of the control of this enzyme by protocatechuate is discussed.
Leucyl‐tRNA Synthetase
Authors: Rouget Pierre , Chapeville François 
Published: March 2005

Two forms of leucyl‐tRNA synthetase of Escherichia coli B were separated and purified about 850‐fold to apparent homogeneity. Their molecular weights were identical, 104000, as determined by Sephadex filtration and polyacrylamide electrophoresis.One of these forms catalyzed the leucine‐dependent ATP‐PPi exchange reaction but was unable to transfer leucine to tRNA even though it could form a complex with tRNALeu. The other form was active for both ATP‐PPi exchange and charge of tRNA.Evidence was obtained for the interconversion between these two forms of leucyl‐tRNA synthetase and for the existence in the E. coli 105000Xg supernatant of a factor stimulating this interconversion; during the incubation of one of these forms with the supernatant, the other form appeared and an apparent equilibrium between the two forms was observed.
Reduction in Immunological Manifestations of 6‐Aminopenicillanic Acid by Treatment with Water‐Insoluble Pronase
Authors: Shaltiel Shmuel , Mizrahi Rachel , Sela Michael , Stupp Yehudit 
Published: March 2005

Penicilloylated proteins which are found as an impurity in 6‐aminopenicillanic acid can be exhaustively digested by pronase to yield amino acids and small peptides. This degradation converts the potent polyvalent antigens into a mixture of mostly monovalent haptens which are much less immunogenic and less capable of eliciting immune reactions in sensitized animals. The degradation of the protein impurity can be carried out in 6‐aminopenicillanic acid preparations, since even a large excess of 6‐aminopenicillanic acid does not appreciably inactivate or inhibit the enzyme.In order to avoid the contamination of 6‐aminopenicillanic acid with a proteolytic enzyme, pronase was converted into a water insoluble form by coupling it with bromoacetyl cellulose or carboxymethyl Sephadex. These insoluble derivatives of pronase were found to retain their activity and broad specificity. Thus, they can be readily removed from the medium upon completion of the impurity degradation, to be used repeatedly in a continuous process.
ATP: Glutamine Synthetase Adenylytransferase from Escherichia coli B
Authors: Ebner Eberhard , Wolf Dieter , Gancedo Carlos , Elsässer Sigrid , Holzer Helmut 
Published: March 2005

Glutamine synthetase adenylytransferase was purified 300‐fold from Escherichia coli B grown on minimal medium. The purified enzyme was found to be homogeneous in the ultracentrifuge, but by electrophoresis on polyacrylamide gel two enzymatically active protein components were separated, that differed from batch to batch in their relative proportions.The apparent Km values of the various substrates and activators of the adenylylation of glutamine synthetase were determined.The adenylylating enzyme requires Mg2+ or Mn2+ and ATP for activity. Several other divalent cations and nucleotides were tested and found to be ineffective. In the presence of glutamine the rate of the reaction decreases at ATP concentrations greater than 1 mM. Addition of ADP, CTP, UTP and ITP to the standard assay mixture, containing ATP results likewise in a decrease of the rate of the reaction. Various intermediates of glycolytic pathway and Krebs cycle inhibit the adenylylation reaction. The optimum pH for adenylylation is about 7.6. The activation energy for the adenylylation was estimated from rate measurements. It is 13 kcal/mole in the temperature range from 5° to 32°. Gel filtration on Sephadex G‐150 indicates an average molecular weight of 145000 daltons. On storage of the enzyme in solution inactive aggregates of higher molecular weight are formed. Bovine serum albumin prevents inactivation and aggregation.
ESR‐ und CD‐Spektren von pH‐abhängigen Konformationsisomeren des Hämoglobin(III)
Authors: Gersonde Klaus , Wollmer Axel 
Published: March 2005

The native horse haemoglobin(III) forms two different pH‐dependent detergent associates. These two associates were related to the existence of two conformation isomers of the protein [11]. By aid of the direct verification of the conformation isomers on the native haemoglobin(III) the possibility should be excluded that the observed associates both originate from only one haemoglobin conformation, which undergoes a pH‐depending transformation of the protein structure in the course of the detergent association.ESR und CD techniques confirm the existence of two isomers of the native haemoglobin. According to these findings haemoglobin(III) is a heterotropic allosteric protein, in which one (at room temperature) or two (at 77° K) proton binding sites interact with the binding site of the 6th ligand mediated by conformation. This interaction can directly be demonstrated in the ESR spectrum of the OH‐derivative by the appearance of distinct signals for both isomers (g′1= 2.68, g′2= 2.16, g′3= 1.82; g″1= 2.68, g″2= 2.14, g″3= 1.77).The allosteric and protolytic reactions are described as a circuit process. By aid of computer simulation model curves are calculated, which allow determination of the actual allosteric and protolytic pK‐values. A simulation of the pH‐dependency of the ellipticity at 340 and 290 nm fits the experimental data, if allosteric pK‐values of 7.2 and 7.0 and protolytic pK‐values of 8.3 and 8.5 are presumed.The α‐helix content remaining constant in the pH‐range concerned, the change of conformation affects the tertiary structure only.Because of the common pH‐dependency the further three low spin signals (g1= 2.91, g2= 2.23, g3= 1.95) have to be attributed to the H2O‐Hb(III) in addition to the high spin signals (g′= 5.9, g′= 2.0), which characterize the low spin part in the physical high spin‐low spin equilibrium of this complex.Further the origin of the conformational active CD bands is discussed.
Peptide Chain Initiation in Homologous and Heterologous Systems From Mitochondria and Bacteria.
Authors: Sala Francesco , KÜNTZEL Hans 
Published: March 2005

Native ribosomal subunits from mitochondria of Neurospora crassa bind fMet‐tRNA and synthesize fMet‐puromycin at 5 mM Mg 2+. The reactions are stimulated by the trinucleotide ApUpG and by GTP. After washing the subunits with 1 M NH4CI the binding capacity is lost but can be restored by adding initiation factors from Escherichia coliUnwashed mitochondrial 73 S ribosomes require E. coli initiation factors for binding fMet‐tRNA and forming fMet‐puromycin. Cytoplasmic 77 S ribosomes from Neurospora are inactive in these chain initiation reactions, even in the presence of bacterial initiation factors.The requirement of the initiation reactions for AUG, GTP and initiation factors is similar in systems from E. coli, Bacillus subtilis and Neurospora mitochondria.Ribosomes and initiation factors from E. coli and B. subtilis are completely interchangeable.The results suggest that mitochondria from Neurospora use a bacteria‐like chain initiation mechanism.
On the Antigenic Determinants of Glutamic‐Aspartic Transaminase
Authors: Patramani Iphigenia M. , Katsiri Katherine D. , Dimitropoulos Constantin G. , Kalogerakos Theodoros G. , Pavlatos Mary P. , Evangelopoulos Athanasios E. 
Published: March 2005

Tryptic hydrolysates of denaturated glutamic‐aspartic transminase fractionated on a Sephadex G‐25 column, gave an elution diagram containing six main fractions. When peptide maps were developed from the transaminase digest 37 spots were detected on the paper sheet.
It was demonstrated that the transaminase fractions (groups of peptides) as well as well as some of the individual peptides eluted from the map spots, possessed immunological activity. This was proved by their capacity to interact with rabbit pig heart antienzyme and rabbit antiserum against the pig‐heart whole tryptic transaminase hydrolysate as well as to inhibit the homologous transaminase‐antitransaminase reaction. Higher immunological reactivity was foud among peptides moving faster in electrophoresis and chromatography.
The catalytic activity of rabbit transaminases (heart, liver, skeletal muscles), was inhibited to a substantial degree by the rabbit anti‐pig heart transaminase. The above enzymes however, as was otherwise expected, gave negative precipitin reactions with antitransaminase. A comparative study of the reactivity between transaminases from pig, ox and rabbit and rabbit anti transaminases against pig and ox heart enzymes as well as against pig‐heart whole tryptic transaminase hydrolysate is presented here.