bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyanogen Bromide Peptides from the αl‐Chain of Cod Skin Collagen
Authors: Laszlo F. , Olsen B. R. 
Published: March 2005

The α1‐chain of cod skin collagen has been cleaved with cyanogen bromide.
The resulting peptides have been isolated and purified by chromatography on phosphocellulose and CM‐cellulose and gel filtration on Sephadex.
The amino acid composition and molecular weights of eight of these peptides, accounting for about 70% of the whole α1‐chain, are presented.
Comparison of amino acid compositions suggests a homology between three of these peptides and cyanogen bromide peptides from rat skin and chick bone α1‐chains.
Effects of Bromopyruvate on the Control and Catalytic Properties of Glutamate Dehydrogenase
Authors: Baker J. P. , Rabin B. R. 
Published: March 2005

When assayed with NAD, the time course of inactivation of glutamate dehydrogenase by bromopyruvate is biphasic. This analyses as two simultaneous first order reactions: the faster corresponds to destruction of an NAD activating site and the slower to the destruction of the active site. Both reactions are first order in bromopyruvate and both sites are protected by combinations of coenzymes and regulators.
When assayed with NADP, activity loss is essentially a single first order process. When ADP is included in this assay, the activity loss profile is similar to that observed with NAD. With GTP included in this assay, the activity first increases, corresponding to a partial loss of GTP response, and then falls off in a first order reaction. The loss of response to both regulators is analysed in terms of a model in which approximately 50% of the regulatory sites are lost in a first order reaction.
Evidence is presented that the sites binding ADP and GTP are not identical.
Effect of ATP on the Oxidation of Succinate in Rat Brain Mitochondria
Authors: Tuena M. , Gómez‐Puyou A. , Peña A. , Chávez E. , Sandoval F. 
Published: March 2005

The effect of ATP on the aerobic oxidation of succinate and on the succinic dehydrogenase activity of isolated rat brain mitochondria has been studied.

The addition of dinitrophenol to brain mitochondria with succinate as substrate produced a small activating effect of oxygen uptake which was followed by inhibition of respiration; the further addition of ATP produced a high rate of respiration.
This effect of ATP was enhanced by added Mg++ and oligomycin and was diminished, but not abolished, by inorganic phosphate.
Experiments were conducted which indirectly indicated that oxaloacetate may be involved in the inhibition of the aerobic oxidation of succinate in fresh brain mitochondria incubated with dinitrophenol; however, attempts to find out if ATP removed oxaloacetate through a particular ATP requiring metabolic pathway were unsuccessful.
In aged, sonicated, and frozen and thawed brain mitochondria incubated with dinitrophenol, ATP still activated the aerobic oxidation of succinate.
The assay of succinic dehydrogenase (EC 1.3.99.1) in aged brain mitochondria revealed that ATP diminished the Km for succinate and increased the Vmax of succinic dehydrogenase. ATP also produced a shift in the pH optimum of succinic dehydrogenase and a partial protection of the enzyme against heat denaturation.
Separation of Two Types of Light Polypeptide Chains from Rabbit γ‐Globulins
Authors: De Vries G. M. , Lanckman M. , Hamers R. 
Published: March 2005

The L chains from rabbit γ‐globulins can be separated by gel filtration into two populations (L1 and L2) differing markedly in their structural and antigenic proporties. The L1 and L2 chains from pooled IgG have different amino‐acid composition and half‐cystine content. In addition, each population can be further resolved in two subfractions called L1a and L1b, L2a and L2b, respectively. The b allotypic markers are located exclusively in L2 chains.These results indicate that the L chains from rabbit IgG are constituted by two populations of different genetic origin.
Biochemistry of the K Antigens of Escherichia coli
Authors: Olson Anita C. , Schmidt G. , Jann K. 
Published: March 2005

Initial work on the determination of the mechanisms of the biosynthesis of the K antigens of E. coli is described. Mutants defective in the biosynthesis of the K‐polysaccharide were used for this study. Acapsular K– mutants were isolated from E. coli 08:K27(A):H– and characterized serologically and through their sensitivity towards specific phages.Previous studies have shown the K27 antigen to be an acidic polysaccharide consisting of glucuronic acid, glucose, galactose and l‐fucose. The 08‐antigen contains mannose as the main constituent of its specific polysaccharide moiety. The influence of mutation on the biosynthetic pathways leading to the K27 polysaccharide was investigated. For this purpose wild strain and various K– mutants were analyzed in this study for the presence of enzymes catalyzing the synthesis of the nucleotide sugar precursors: UDP‐glucose, UDP‐galactose, UDP‐glucuronic acid, GDP‐mannose and GDP‐l‐fucose. The following bacterial enzyme activities were tested in cell free system: hexokinase, phosphoglucoisomerase, phosphoglucomutase, UDP‐glucose pyrophosphorylase, UDP‐galactose‐4‐epimerase, UDP‐glucose dehydrogenase, GDP‐mannose pyrophosphorylase, GDP‐mannose hydrolyase.When two K– mutants were crossed and selections were made for his+, a small but significant number of K+ strains appeared among the recombinants. Thus, it was concluded that the parent K– strains had different blocks in the synthesis of the K27 antigen which mapped at different sites on the chromosome. Repair occurred due to crossing over within a small (his‐linked) region of the chromosome. Biochemically, the repair of the K– character by genetic crossing of the two K– mutants was reflected in the capability for GDP‐l‐fucose synthesis which was deficient in the donor strain as well as in the larger portion of the K– recombinants. In two of the K– mutants all enzymes tested were found to be operative. Since synthesis of the nucleotide precursors was possible, these mutants probably have a defect in the K27 specific transferase system. One K– mutant, which serves as the recipient in the genetic crossing, showed some serological R character. This mutant possessed a very low GDP‐mannose pyrophosphorylase activity; however, some O specific (mannose containing) polysaccharide was formed. Since all other synthetases are active in this mutant it is assumed that also in this case the K27 transferase system may be defective.
Dietary and Hormonal Control of Enzymes of Amino Acid Catabolism in Liver
Authors: Pestaña A. 
Published: March 2005

A high glucose diet fed ad libitum decreased the activities in rat liver of histidase, serine dehydratase, homoserine dehydratase, ornithine transaminase, mitochondrial aspartate transaminase and cytoplasmic alanine transaminase, as compared to normal fed animals.Casein hydrolysate or tryptophan alone given to protein deplted rats increased the hepatic levels of serine dehydratase, alanine transaminase and tyrosine transaminase. Histidase and homoserine dehydratase were increased by casein hydrolysate but not by tryptophan. Aspartate transaminase was increased by tryptophan, but not by casein hydrolysate.Glucose administered intragastrically partly or totally counteracted the induction of serine dehydratase, tyrosine transaminase, cytoplasmic alanine transaminase by cortisol of glucagon administration to protein depleted rats. The similar induction of ornithine transaminase and cytoplasmic aspartate transaminase by cortisol was also counteracted by glucose.
The Subunit Structure of α‐Crystallin
Authors: Schoenmakers J. G. G. , Gerding J. J. T. , Bloemendal H. 
Published: March 2005

The present results, together with physicochemical evidence presented elsewhere, indicate that α‐crystallin from calf lens is composed of two acidic and two basic polypeptide chains. The acidic polypeptides could be isolated by chromatography on SE‐Sephadex at pH 5.5 in the presence of 7 M urea. It could be demonstrated that both S‐carboxymethylated acidic polypeptides are of equal molecular weight and amino acid composition. In both chains N‐acetylmethionyl‐aspartate was found as the N‐terminal and serine as the C‐terminal residue. Peptide mapping reveals one unique peptide region for each polypeptide.In embryonic α‐crystallin only one acidic polypeptide can be detected. From comparative amino acid analysis, peptide maps as well as physicochemical behaviour it may be deduced that the polypeptide present in the early embryonic stages is identical with the adult acidic polypeptide A‐2.
Comparative Structural Studies of the Active Site of ATP‐Guanidine Phosphotransferases
Authors: der Terrossian E. , Pradel L. A. , Kassab R. , Thoai N. V. 
Published: March 2005

The purification and the amino acid sequence of the peptide containing the essential sulphydryl group of arginine kinase from Homarus vulgaris muscle is described.The fractionation of the tryptic digest of arginine kinase labelled with N‐[1‐14C]ethylamaleimide has been carried out using gel filtration, ion‐exchange chromatography and paper chromatography. The composition of the radioactive peptide, isolated from the digest, is reported together with its amino acid sequence. A structural comparison is made between the peptide of arginine kinase and the corresponding active‐cysteine containing peptide isolated from rabbit muscle creatine kinase.
Regulatory Properties of a Plant NAD: Isocitrate Dehydrogenase
Authors: Coultate T. P. , Dennis D. T. 
Published: March 2005

Some properties of NAD: isocitrate dehydrogenase from swede (Brassica napus L.) are described. This enzyme shows simpler regulatory properties than that from animals or fungi.
Isocitrate, citrate and tricarballylate are positive effectors but neither ADP nor AMP have any effect. Pyruvate, acetate, α‐ketoglutarate, succinate and dl‐malate do not stimulate or inhibit at 2 mM.
ATP and other nucleoside triphosphates inhibit this enzyme but the inhibition appears to be due to the formation of a complex with the activating cation.
The principal control of the enzyme is a potent inhibition by NADH competitive with NAD. Elevation of either isocitrate or activating cation concentration lowers the Km for NAD and in this respect MnSO4 is more effective than MgSO4. In contrast, the Ki for NADH is 0.05 mM with 1 mM MgSO4 and 0.16 mM with 1 mM MnSO4.
The enzyme is inhibited by high concentrations (> 20 mM) of inorganic anions. This inhibition is apparently competitive with isocitrate but anions most likely cause a conformational change.
The interactions between isocitrate and activating cation have been examined. Elevation of the concentration of either isocitrate or cation raises the affinity of the enzyme for the other to a limiting value. The nature of the cation has only a slight effect on the minimum Km for isocitrate (0.35 mM with MgSO4, 0.25 mM with MnSO4) but the minimum value of the Km for MgSO4 is 100 μM compared with 7 μM for MnSO4.
It is concluded that the enzyme binds one molecule each of isocitrate, activating cation and NAD or NADH at the catalytic site and one molecule of citrate or isocitrate at an effector site.
Sur la biosynthèse de la chaîne latérale éthyle des stérols du Myxomycète Dictyostelium discoideum
Authors: Lenfant M. , Ellouz R. , Das B. C. , Zissmann E. , Lederer E. 
Published: March 2005

Previous work of several laboratories has shown that the two carbon atoms C‐28 and C‐29 of the ethyl or ethylidene side chains of phytosterols are introduced on a C‐24 unsaturated side chain by two successive C‐methylation steps. A scheme, based on previous work of Nes et al. and Goodwin et al., gives the various intermediates which can be formed by stabilisation of the intermediate carbonium ion (II). It was usually thought that ethylidene compounds such as (III) were the precursors of ethyl compounds such as (VIII) and this has been proved recently in the case of poriferasterol (IX) which contained four deuterium atoms when Ochromonas malhamensis was grown in presence of [Me‐2H3] methionine [8].In the present paper it is reported that the sterol of the slime mold Dictyostelium discoideum [Δ 22‐stigmasten‐3‐β‐ol (Xa)] contains five deuterium atoms, when extracted from D. discoideum fed on cells of a methionine‐less strain of E. coli grown in presence of [Me‐2H3] methionine. The unsaturated sterol (Xa) is accompanied by the saturated sterol (XIa) which was not previously found in this organism.Mass spectrometry of the pentadeuterated sterols (Xa) and (XIa) seemed to show conclusively that all five deuterium atoms are located in the ethyl side chain [11], but it was thought necessary to confirm this conclusion by a detailed analysis of the side chain; thus, the sterol (Xa) was ozonised and part of the side chain isolated as a crystalline p‐phenylphenacyl ester (XIIIa). Mass spectrometry of this compound and of a synthetic non‐labelled (XIIIb) and the corresponding monodeuterated derivative (XIIIc) confirms that all five deuterium atoms of the Dictyostelium sterol (Xa) are in the ethyl side chain.These results exclude an ethylidene compound (such as III) as a precursor of the sterol (Xa); they do not allow us to choose between other possible routes illustrated in the scheme. Our experiments also show that there is no hydrogen shift during the second methylation step.
The Purification and Properties of Cytidine Aminohydrolase from Sheep Liver
Authors: Wisdom G. B. , Orsi B. A. 
Published: March 2005

Cytidine aminohydrolase was purified about 280‐fold with an overall 8% yield from the cytoplasmic fraction of sheep liver cells by the use of protamine sulphate precipitation, salt fractionation using trisodium citrate, acidification and chromatography on DEAE‐and CM‐celluloses.The enzyme catalyses the deamination of several aminopyrimidine nucleosides. Its pH optimum occurred at 5.0 and it was relatively acid and heat stable. The high sensitivity of the enzyme to compounds known to react with sulphydryl groups and the presence of a substrate‐binding group of pKa 9.2 in the enzyme suggests that a sulphydryl group may be important in the catalytic process. dTTP and dUTP were found to inhibit and dCTP to activate the enzyme respectively. The complex type of inhibition produced by dTTP indicates that this aminohydrolase may have a regulatory role similar to that of dCMP aminohydrolase.
Determination of the N‐Terminal Amino Acids in Proteins Using Fluoro‐Nitropyridines
Authors: Signor A. , Biondi L. , Tamburro A. M. , Bordignon E. 
Published: March 2005

A new procedure for the determination of the N‐terminal groups in peptides and proteins is described. The free amino‐groups are allowed to react with 2‐fluoro‐3‐nitropyridine or 2‐fluoro‐5‐nitropyridine in slightly alkaline solution; the resulting derivatives are easily hydrolyzed in dilute hydrochloric acid in sealed tubes to give the corresponding nitropyridyl amino acids. Most of these compounds are quantitatively recovered under these conditions: in particular it is possible to estimate proline and glycine as N‐terminal residues.After isolation the nitropyridyl amino acids can be estimated spectrophotometrically; in some cases it is possible to regenerate the parent amino acid by treating the derivatives with strongly alkaline solutions. The adequacy of the present techniques in relation to those of other workers was tested on insulin, lysozyme and aldolase; the advantages and peculiarities in comparison with these procedures are discussed.
Studies on Renin with Synthetic Substrates
Authors: Reinharz A. , Roth M. 
Published: March 2005

Renin has been shown to catalyze the hydrolysis of the protected octapeptide, Z‐Pro‐Phe‐His‐Leu‐Leu‐Val‐Tyr‐Ser‐β‐naphthylamide, at the leucyl‐leucyl bond. When the octapeptide substrate is incubated with renin and an excess of the auxiliary enzyme, aminopeptidase M, the fluorescent β‐naphthylamine is liberated at a rate related to renin concentration. A chemical assay of renin based on these facts is described in detail. When assayed with this method, kidney renin from man and pig shows pH optima of 5.4 and 5.7 respectively. Renin from submaxillary glands of mice, which also attacks the substrate, is optimally active at pH 5.4.The limit of sensitivity of the assay is 0.001 Goldblatt units for human renin and 0.01 Goldblatt units for pig renin. Trials with other possible synthetic substrates showed that Z‐Pro‐Phe‐His‐Leu‐Leu‐β‐naphthylamide is poorly hydrolyzed by renin, and Z‐Leu‐Leu‐β‐naphthylamide not at all.
Changes in the Short Wavelength Absorption Spectrum of Tyrosine as a Result of its Participation in Peptide, or Similar Bonds
Authors: Delius A. E. , Franze de Fernández M. T. , Paladini A. C. 
Published: March 2005

The perturbation of the spectrum of free tyrosine that occurs when this amino acid is combined to other amino acids or in the form of acetyl derivative, acetyl derivative amide or acetyl derivative ethyl ester was studied.
The difference spectrum of each compound was obtained by measuring the absorbance of its solution against that of a mixture of its component free amino acids.
A red‐shift of the 2,400 Å absorption band, in 0.1 M NaOH, or 2,230 Å, at pH 7, was clearly detected.
Maximum perturbation is produced when tyrosine has both its amino and carboxyl groups involved in peptide bonds.
Coenzyme Binding in Yeast Pyruvate Decarboxylase
Authors: Wittorf John H. , Gubler Clark J. 
Published: March 2005

The formation of a fluorescent complex between apopyruvate decarboxylase of Saccharomyces carlsbergensis and thiochrome pyrophosphate, a competitive inhibitor with thiamine pyrophosphate, and Mg(II) ions is reported. A similar complex between thiochrome and the apoenzyme could not be detected, demonstrating the importance of the pyrophosphate group of the coenzyme in binding to the protein. Complex formation between the apoenzyme and thiochrome pyrophosphate in the absence of Mg(II) could also not be demonstrated. The role of magnesium in coenzyme binding is discussed, especially in reference to interaction with the pyrophosphate moiety. The apparent Km for Mg(II) ions, after correction for residual apoenzyme activity, is reported to be 87 μM.The shift in the fluorescence emission spectrum of thiochrome pyrophosphate of 23–24 nm toward lower wavelengths, upon complex formation, coincided with the behavior of thiochrome in solvents of lower polarity than water. A hydrophobic region at the coenzyme binding site of pyruvate decarboxylase is proposed. Enhancement of thiochrome fluorescence occurred concomitantly with the blue shift in the emission spectrum upon complex formation.The excitation wavelength of 290 nm employed to demonstrate complex formation suggested energy transfer from the tryptophan to the thiochrome chromophore. Quenching of fluorescence in the 340–350 nm region, however, occurred not only in the protein emission spectrum upon complex formation, but also when free tryptophan and thiochrome interacted with each other. The quenching of the protein fluorescence appears to be independent of hydrophobic interaction at the coenzyme binding site. It is suggested that protein tryptophan residues relatively exposed to solvent interact individually with the thiochrome molecule by an energy transfer mechanism to produce the quenching in pyruvate decarboxylase.
Specific Dissociation of Ribosomes from Saccharomyces cerevisiae by a Protein Factor
Authors: Pêtre Jean 
Published: March 2005

A ribosome fraction enriched in “native” subunits by differential centrifugation yields, upon washing in a buffer containing ammonium chloride and magnesium ions, a protein mixture which can dissociate cytoplasmic ribosomes from Saccharomyces cerevisiae into 40 S and 60 S subunits.This heat dependent reaction cannot be related to any marked ribonuclease activity in the protein mixture.Furthermore, the mixture is unable to dissociate Escherichia coli or rabbit reticulocyte ribosomes; this property is unique, since proteolytic enzymes readily dissociate reticulocyte ribosomes as well as yeast ribosomes.Within 30 min of incubation, the factor‐dependent dissociation reaches a plateau, due either to the stoichiometric mode of action of the factor, or to the inability of ribosomes to support complete dissociation under the ionic conditions of the experiments.These two points are discussed.
Relations structurales entre les acides mycoliques insaturés et les acides inférieurs insaturés synthétisés par Mycobacterium phlei
Authors: Asselineau Cécile P. , Lacave Charlotte S. , Montrozier Henri L. , Promé et Jean‐Claude 
Published: March 2005

Mycobacterium phlei synthesizes a complex mixture of saturated and unsaturated fatty acids, with a normal or a branched chain. We have isolated the unsaturated fatty acids R–CH = CH–(CH2)n–CO2H, with twenty to twenty seven carbon atoms. These acids only make up a very small amount of the total fatty acids. Their structures were established by means of the oxidation method of Lemieux, followed by gas chromatographic analysis of the lower acids thus obtained.Some of these unsaturated acids (4‐eicosenoic, 6‐docosenoic, 8‐hexacosenoic acids) are likely to be metabolically related, whereas 5‐enoic fatty acids (normal chain 5‐enoic acids with 22, 24 or 26 carbon atoms and branched chain 5‐enoic acids with 25 and 27 carbon atoms) could arise through a common peculiar process.Simultaneously, by use‐of the same oxidation method, we have identified the radical R in the mycolic acids R–CH = CH–X–CH(OH)–CH(R')–CO2H. These radicals R are identical to the radicals R of the five different 5‐enoïc fatty acids. This observation suggests the hypothesis that these unsaturated acids play a role in the synthesis of the mycolic acids in Mycobacterium phlei. By a critical analysis of previous work in this field, we show that this hypothesis is consistent with all the results found in the literature.
Horse Liver Alcohol Dehydrogenase
Authors: Jörnvall Hans 
Published: March 2005

The ethanol‐active isoenzyme of horse liver alcohol dehydrogenase has been carboxymethylated with iodo[14C]acetate and different samples of the labelled protein treated with trypsin (both with and without previous maleylation of the substrate), chymotrypsin, pepsin or cyanogen bromide. In each case most of the resultant peptides have been purified and characterized.
Data are given for those peptides originating from an N‐terminal region comprising about 40% of the protein chain and the amino acid sequence of the first 140 residues is deduced.
It is established that over this region the two chains of the enzyme have an identical sequence. The N‐terminus is an acetylated serine residue and the “active site” cysteine residue occupies position no. 46. One of the two tryptophans of the chain, but none of the four tyrosines, is in the sequence given. The region around position 100 is rich in cysteine residues. Some serine residues were found to have reacted during maleylation of the protein.
The amino acid sequence is compared to the previously known sequences of glyceraldehyde 3‐phosphate dehydrogenase from two species. Similarities strongly suggest a true homology, at least of an N‐terminal region, and support theories of a common ancestral origin for these enzymes. The reactive cysteine residues are, however, at widely different positions in the primary structures.
The Identification of a Reactive Lysine Residue in Lobster Glyceraldehyde‐3‐phosphate Dehydrogenase
Authors: Davidson Barrie E. 
Published: March 2005

Lobster glyceraldehyde‐3‐phosphate dehydrogenase was found to contain a reactive lysine residue that is specifically acetylated when the NAD‐deficient form of the enzyme is incubated with [1‐14C]acetyl phosphate at pH 8.5. The residue was identified by sequence analysis as number 182 in the polypeptide chain of the enzyme.Both the acetylation behaviour and the position of the lysine residue are identical with that found for mammalian glyceraldehyde‐3‐phosphate dehydrogenases. In addition the amino acid sequence around lysine 182 was found to be identical, except for a few conservative changes, with the corresponding sequence in pig glyceraldehyde‐3‐phosphate dehydrogenase.