bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of the Esterase Activity and the Anion Inhibition of Bovine Zinc and Cobalt Carbonic Anhydrases
Authors: Thorslund A. , Lindskog S. 
Published: March 2005

The rates of hydrolysis of nitrophenyl esters, catalyzed by bovine carbonic anhydrase, depend on the position of the nitro group and on the size of the acyl residue. The most rapidly hydrolyzed substrate of those investigated is p‐nitrophenyl acetate. The catalyzed rates are proportional to both enzyme and ester concentrations. Only in the case of m‐nitrophenyl acetate could a value of the Michaelis constant, Km, be estimated, approximately 10 mM. Product inhibition by o‐nitrophenol occurs during the enzyme‐catalyzed hydrolysis of o‐nitrophenyl acetate.
The metal specificity of the enzyme seems to be independent of the substrate. Zn(II) and Co(II) are about equally effective in restoring esterase activity to the apoenzyme while all other metal ions studied do not activate or have a very small effect.
The pH‐dependence of the esterase activity of both Zn(II)‐ and Co(II)‐carbonic anhydrase is very similar to that of the CO2 hydration activity, and the basic form of a group with a pK near 7 is required for both reactions. Anionic inhibitors are strongly bound to the enzyme when this group is in its acidic form, but the inhibition is almost abolished at alkaline pH.
The inhibitory powers of cyanide and sulfide decrease at acid as well as at alkaline pH. The results agree with the assumption that, formally, CN− and HS− do not bind to the basic form of the enzyme, while HCN and H2S do not bind to the acidic form.
The Stereospecificity of the Citrate Synthase in Sulfate‐Reducing and Photosynthetic Bacteria
Authors: Gottschalk G. 
Published: March 2005

The stereospecificity of the citrate synthase of a number of sulfate‐reducing and photosynthetic bacteria was determined by the following method: radioactive citrate was synthesized from [4‐14C]oxaloacetate and acetylcoenzyme A by cell‐free extracts. The resulting citrate was then cleaved to acetate and malate by citrate lyase plus malate dehydrogenase. In the case that the usual citrate synthase was present in the cell‐free extracts, the citrate cleavage yielded radioactive malate and unlabeled acetate. The presence of the Clostridium kluyveri type of citrate synthase led to the formation of radioactive acetate and unlabeled malate.It was found that four species of the Athiorhodaceae, Desultfovibrio gigas, D. sale xigens and Desulfotomaculum ruminis contain the usual citrate synthase. Two strains of D. desulfuricans and two strains of D. vulgaris contain the C. kluyveri type of citrate synthase, which is now referred to as (R)‐citrate synthase.The presence of the (R)‐citrate synthase in D. desulfuricans and D. vulgaris was confirmed by an in‐vivo experiment. When grown on pyruvate and radioactive carbon dioxide, the protein of these two species contains [5‐14C]glutamate, whereas the protein of D. gigas contains [1‐14C]‐glutamate.The presence of the (R)‐citrate synthase in certain strictly anaerobic bacteria is discussed from an evolutionary point of view.
Lysolecithin‐Stoffwechsel in Erythrocytenmembranen
Authors: Ferber E. , Munder P. G. , Kohlschütter A. , Fischer H. 
Published: March 2005

Human erythrocytes have a life span of about 120 days. One can easily separate young and aged cells by density centrifugation. For these reasons they are especially suited for studying ageing processes.There is general agreement that the activity of several glycolytic enzymes decreases during ageing. However, nothing is known about typical membrane enzymes in connection with ageing, and since it was felt that membrane alterations might be of primary importance, a comparative study of phospholipid‐metabolizing enzymes was undertaken.The enzymes studied in this investigation were:a) the structure‐bound acid: CoA ligase (AMP) and acyl‐CoA: Iysolecithin‐O‐acyltransferase which together incorporate lysolecithin and fatty acid into membrane bound lecithin.b) lysophospholipase (lysolecithin acyl‐hydrolase) which degrades lysolecithin into glycerophosphorylcholine plus fatty acid.Human erythrocytes from healthy donors were separated by simple ultracentrifugation and by albumin density centrifugation according to age. The mean volume of the young erythrocytes was 109 μ3, while that of the aged cells was 74 μ3. The enzyme activities of freeze‐thawed cells were determined and corrected for cell numbers. Furthermore, the enzyme activities‐in hemoglobin‐free stroma were measured.[14C]‐labelled substrates were used to determine the enzyme activities: [1‐14C]oleic acid for the acylation of lysolecithin and [1‐acyl‐14C]lysolecithin for the lysophospholipase reaction.The results showed that the activities of both enzymic reactions as measured with old cells were 40 to 50% lower than the activities found in young cells. In hemolysates from young and old cells the following enzyme activities were determined: the acylating activity decreased from 117 to 67 MolX10−20/cell×min, and the lysophospholipase activity from 185 to 123 Mol×10−20/cellXmin.The ATP content of old cells was only slightly lower than that of young cells.Comparative analyses of erythrocytes stored in acid citric dextrose for two months at 4° gave different results: these cells which had been “aged in vitro” had an extremely low ATP content, while the activities of the lysolecithin metabolizing enzymes remained unchanged.These findings suggest that the lysolecithin metabolism has a significance in cell ageing processes. It remains to be shown, however, that lysolecithin produced by macrophages lining the RES sinuses is the decisive factor responsible for the death and removal of aged cells.
The Effect of Piericidin A on Energy‐Linked Processes in Submitochondrial Particles
Authors: Vallin I. , Löw H. 
Published: March 2005

Piericidin A inhibits the oxidative phosphorylation capacity of the NADH oxidase in submitochondrial systems at concentrations of 30 pmoles/mg protein, that of the succinic oxidase at 6 nmoles/mg protein and the phosphorylation in the cytochrome oxidase region at concentrations of 5 μmoles/mg protein.
The energy dependent NAD+ reductions are 10 times more sensitive to piericidin A than the NADH oxidase reaction. There is a correlation between the oxidation reduction state of the respiratory chain components, presumably of coenzyme Q and the extent of sensivity to the inhibitor.
Piericidin A and guanidine compounds showed an additive or more than additive inhibitory effect when added together.
p‐Chloromercuribenzoate and piericidin have a synergistic effect when added simultaneously. 2, 3‐Dimercaptopropanol (BAL) could partly release the piericidin inhibition, in contrast to glutathione, indicating an involvement of proximal –SH‐groups in the piericidin sensitive site.
Some discrepancies between the piericidin action and the inhibitory action of rotenone and amytal are noted.
A hypothesis is put forward for the possible interaction of a non‐heme iron component, structurally arranged by S‐bonds and coenzyme Q and the relevance of this chelate for the generation of a primary high energy complex.
Effects of Ultraviolet Irradiation (2537 Å) on the Structure of Human Thyroglobulin
Authors: Vecchio G. , Salvatore G. , Dose K. 
Published: March 2005

The effect of in vitro ultraviolet irradiation at 2537 Å on the structure of highly purified human thyroglobulin has been investigated by following the ultracentrifugal pattern and the appearance of free sulfhydryl groups in the irradiated protein.Thyroglobulin (19 S) dissociates into two 12 S subunits when it is irradiated with doses of a few hundred Einsteins per mole. The quantum yields of dissociation vary between 0.5 × 10−3 and 2 × 10−3, depending on the experimental conditions. At higher ultraviolet doses, the protein is partially aggregated and denatured.The extent of dissociation is largely dependent on the ionic strength and the pH of the medium. Doses up to 1,500 Einsteins per mole cause only a partial (30%) splitting of the 19 S molecules, at neutral pH in 0.1 M KCl, whereas at pH 10 and low salt (Γ/2=0.0042), the same dose produces almost complete dissociation into 12 S subunits.Ultraviolet light also causes the rupture of some of the disulfide bonds of native thyroglobulin. On irradiation with several hundred Einsteins per mole protein, as many as 21 –SH groups per molecule can be titrated. The quantum yields for –SH production and destruction of cystine residues are both 0.05.No direct correlation has been found between the extent of dissociation of thyroglobulin and the number of –S–S– bonds cleaved, nor between the reassociation of the 12 S subunits and the reoxidation of –SH groups. It is concluded that two 12 S units present in human thyroglobulin are not linked by interchain disulfide bridges; the disulfides cleaved by ultraviolet irradiation, however, may play an important role in maintaining the subunit organization of the protein molecule.
Carotenoids in the Carapace of the Orconectes limosus (Raf.), Crustacea: Decapoda
Authors: Czeczuga B. , Czerpak R. 
Published: March 2005

The presence of carotenoids in Decapoda‐Orconectes limosus (Raf.) was studied.
In extracts from carapace Orconectes limosus1 separated by means of column and thin‐layer chromatography, the following carotenoids were identified: β‐carotene, echinenone, lutein (epoxide and ester), astaxanthin (free and ester) and one unknown xanthophyll.
Bovine Liver Homogentisicase: Apo‐ and Reconstituted Holoenzymes
Authors: Takemori S. , Furuya E. , Mihara K. , Katagiri M. 
Published: March 2005

Bovine liver homogentisicase can exist in two forms which are interpreted as being apo‐and holoenzymes. It is obtained in an unenriched form (apoenzyme) from bovine liver by acetone and ammonium sulfate fractionations and chromatography on hydroxylapatite column. This form of the enzyme can be enriched to an active form (holoenzyme) by incubation with ferrous ion under anaerobic conditions. The extent of activation is completely time dependent and the rate is extremely sensitive to the pH. Reducing substances do not affect the restoration of activity of the apoenzyme under anaerobic conditions. Properties of the apo‐ and holoenzymes are compared with respect to absorption spectrum, effects of reducing agents and pH on activity (or on reconstitution), stability, and molecular weight.The activity of homogentisicase is strongly inhibited by various diphenolic compounds as well as chelating agents specific for ferrous ion. However, the reconstitution of homogentisicase from the apoenzyme with ferrous ion is strongly prevented only by the substrate, homogentisate or 2,5‐dihydroxybenzoate, a compound structurally similar to the substrate.
Molecular Classes and Properties of Antibodies in Cattle Serum and Colostrum Synthesized during the Primary and Secondary Response to Protein Antigens
Authors: Hammer D. K. , Kickhöfen B. , Henning G. 
Published: March 2005

The kinetics of the antibody response in cattle have been analyzed and the following results were obtained:

A single administration of proteins to cattle given intravenously or as alum‐precipitated antigen evoked a concurrent synthesis of γM‐ and γG‐antibodies as reflected in the serum 7 days following immunization. Employing the antigen binding capacity method for assaying antibody activity, the γG‐antibody collected 7 days after immunization exceeded by several times that of the γM‐class.
The γG‐antibody response as reflected in serum and colostrum three weeks after primary stimulation showed a marked increase when compared with their respective antibody levels formed earlier. The colostral 19 S antibody, composed of 19 S γG‐globulin and the easily discernible γM‐component was also increased and surpassed by several times the γM‐antibody level in a 3‐weeks serum.
When colostrum was fed to the newborn calf, the γG‐antibody appeared to be absorbed quantitatively by the intestinal tract, whereas the high molecular weight globulins (19 S) were transmitted much less efficiently. This might indicate that some sort of selective absorption occurred between different classes of immunoglobulins.
Kinetic studies of the secondary response demonstrated that in cattle serum an anamnestic reaction exists for γM‐antibody as well as for γG‐antibody.
The dissociation of the 19 S molecules from serum and colostrum by reduction and alkylation produces little effect on the antigen binding capacity of the monomer subunits obtained.
The kinetic characteristics of serum and colostral 19 S‐ and γG‐antibodies were studied by measurement of the association rates. γM‐Antibodies present in serum 7 days following antigenic challenge had a higher affinity for protein antigens than γG‐antibody molecules. There is considerable evidence, however, that the affinity of the γG‐antibody for the antigenic determinants increased progressively with time after immunization.
Immunochemical Studies on Salmonella
Authors: Fuller N. A. , Etievant M. , Staub A.‐M. 
Published: March 2005

The wild strain of Salmonella cholerae suis carries the O‐antigen specificities 62 and 7. The phage converted strain has specificities 62, (7) and 14.Four serologically active oligosaccharides can be isolated from the O‐antigenic polysaccharide of the phage converted strain of S. cholerae suis 62, (7) 14; their general formula is (Man)n→ Man → GlcNAc ↑ Glc where n ↑ 0, 1, 2 or 3. Data from precipitation inhibition studies using rabbit antisera indicate that there are several fractions of antibodies (anti 62, 7, 14) all directed against the same terminal (= immunodominant) sugar trait, i. e.d‐glucose. Chemical analysis shows that there is only one terminal non‐reducing glucose residue per “repeat unit”, both in the wild and converted strains. The position of the glucose residue, however, on the oligomannose chain is different in the wild and converted strains. It is established therefore that the change in antigenic specificity (appearance of factor 14) brought about by phage conversion of S. cholerae suis is correlated with the new and definite position of d‐glucose on the oligomannose chain.
The Properties of Molecular Fragments Obtained on Treating Calfskin Collagen with Collagenase from Clostridium histolyticum
Authors: Stark M. , Kühn K. 
Published: March 2005

Collagenase was found to attack the collagen molecule at both ends at 10°. Six molecular fragments of different lengths were observed and could be correlated with the intact molecule as long‐spacing segment fragments. It was possible to isolate the 2,600,1,250 and 780 Å fragments by fractional ammonium sulphate precipitation.The sharp helix‐coil transition on denaturation shows that the fragments have an intact triple helix. It was possible to separate the two shorter fragments into three components (the α1, α2 and α3 chain fragments) by chromatography on CM cellulose. The α1 and α3 chains have very similar amino acid compositions and peptide maps for both these fragments. This suggests that the differences between these two components are probably due to telopeptides and not to the amino acid sequence of the main chain.
Metal‐Combining Properties of Human Lactoferrin (Red Milk Protein)
Authors: Masson P. L. , Heremans J. F. 
Published: March 2005

Human lactoferrin, the red iron‐binding protein from milk, was prepared by chromatography on DEAE‐cellulose of the milk proteins soluble in 2 M ammonium sulfate. Several preparations differing in iron content were obtained. Apolactoferrin was prepared by dialyzing the protein against 0.1 M citric acid.Saturation experiments with iron ascorbate indicated the iron: protein ratio at saturation to be 0.025 micromoles of metal per mg of protein. Assuming 80,000 to be the molecular weight of lactoferrin, this would correspond to a ratio of two iron atoms per molecule. With copper, a similar molar proportion at saturation was obtained. Gasometrie measurements were used to calculate the amount of carbon dioxide liberated upon dissociation of the metal‐protein complexes by acidification. One mole of CO2 was freed per atom of iron or copper.
Isoenzymes of Malate Dehydrogenase in Saccharomyces cerevisiae
Authors: Atzpodien W. , Gancedo J. M. , Duntze W. , Holzer H. 
Published: March 2005

Extracts from yeast cells grown under different conditions and from mitochondria were subjected to agar gel electrophoresis. Three bands showing malate dehydrogenase activity were found in extracts from aerobic derepressed cells (c‐MDH I, c‐MDH II, and m‐MDH III), whereas generally only one band was present in extracts from anaerobic repressed cells (c‐MDH I) and another one in extracts from mitochondria (m‐MDH III) of aerobic derepressed cells.The different malate dehydrogenases showed dissimilar regulatory and physical properties, e. g. sensitivity to inactivation by heat, inhibition by oxaloacetate and by p‐chloromercuribenzoate, activation by Pi, Michaelis constants etc. A separation of malate dehydrogenases by DEAE‐cellulose chromatography was performed giving only two malate dehydrogenase forms. These two forms were subjected to agar gel electrophoresis and gave one band each, corresponding to the cytoplasmic c‐MDH I and c‐MDH II. The possible metabolic significance of the three malate dehydrogenase isoenzymes is discussed.
Oxidation of n‐Hexadecane by Subcellular Preparations of Guinea Pig Small Intestine
Authors: Mitchell M. P. , Hübscher G. 
Published: March 2005

A method is described for the quantitative assay of the conversion of [1‐14C]n‐hexadecane to palmitic acid using gas‐liquid chromatography with [1‐14C]heptadecanoic acid as internal standard.
Subcellular preparations of the mucosa of guinea pig small intestine were found to convert n‐hexadecane to palmitic acid. The oxidation system was located mainly in the microsomal fraction (8,400,000 ×g× min) but there was definite activity also in the high‐speed supernatant (8,400,000 ×g× min). The possible involvement of microbial enzymes from the flora of the small intestine was excluded.
Factors affecting the conversion were studied with the microsomal fraction and with a low‐speed supernatant (377,000 ×g× min). Substantial conversions were obtained in the presence of NAD or an NADPH‐generating system separately, but maximum conversion was only obtained when these were present together. When air was replaced by carbon monoxide the conversion was inhibited by 42%.
Labelled n‐hexadecanol was detected as an intermediate and was also shown to be oxidised to palmitic acid.
The role of the enzyme system is discussed in relation to the occurrence of n‐alkanes in the diet and their absorption from the small intestine.
Sur la biosynthèse de la piloquinone, o‐phénanthrène‐quinone produite par Streptomyces pilosus
Authors: Zylber J. , Zissmann E. , Polonsky J. , Lederer E. 
Published: March 2005

Piloquinone (m.p. 178°, C21 H20 O5), the principal pigment produced by Streptomyces pilosus had been isolated in 1963 in our laboratory and its structur determined [1, 2]. It is a 2‐methyl‐3‐iso‐caproyl‐1, 8 dihydroxy‐9, 10 phenanthrene quinone (I).Quinones of this type are very rare in nature; for one of these: denticulatol (II) Birch has proposed a biosynthetic pathway from polycetate.For piloquinone two biosynthetic schemes had been proposed [2]:a) isocaproyl‐ or isobutyryl‐CoA could condens with respectively eight or nine acetate units to give precursor VIII, which would be transformed into piloquinone (I) by decarboxylation, cyclisation and appropriate modifications of the oxidation level;b) propionyl‐CoA could condense with nine units of acetate to give the precursor IX which, after C‐methylation, would lead again to VIII. This latter hypothesis had been proposed because ɛ‐pyrromycinone (X) is fromed by way of the same intermediate (IX).The following precursors were added to growing cultures of Streptomyces pilosus: [1‐14C]‐acetic acid, [1‐14C]propionic acid, [1‐14C]isobutyric acid, [U‐14C]valine, [14C‐methyl]methionine and [2‐14C]mevalonic acid.Piloquinone (I) incorporated radioactivity from acetic acid, isobutyric acid, isocaproic acid and valine, but did not incorporate radioactivity from methionine, propionic acid, or mevalonate.These results confirm hypothesis (a) and seem to exclude pathway (b).In view of localizing the radioactivity in piloquinone isolated from cultures grown in presence of isocaproic acid, isobutyric acid or valine, the leuco‐acetate derivative of piloquinone was submitted to a Baeyer‐Villiger oxidation giving the tetraacetate‐ester XII. After hydrolysis, radioactive isocaproic acid was isolated as its p‐phenyl‐phenacylate.Table 2 shows that it contains 11.8% of the radioactivity of piloquinone when [1‐14C]acetate was the precursor, and 93 or 98% when [U‐14C] valine or [1‐14C]isobutyrate were the precursors. These results show that isobutyrate (as such, or formed from valine) is the “starter” of the side chain of piloquinone whereas the rest of the carbon skeleton comes from polyacetate.It seems that our work is the first experimental proof showing that phenanthrene derivatives can also be synthetised in vivo from a polyacetate precursor.
Spectroscopic Differentiation of the Electron‐Accepting Sites in Fungal Laccase
Authors: Malmström B. G. , Vänngård T. , Malkin R. 
Published: March 2005

The difference specrum between oxidized and reduced fungal laccase at pH 5.5 shows an absorption band at 330 nm in addition to the visible absorption band at 610 nm.
The 610 nm band and the 330 nm band are reduced together in a linear fashion with the addition of 3.5 electron equivalents of ascorbate.
Titration of laccase in the presence of 3 mM fluoride leads to a differentiation of the electron‐accepting site in the molecule. The 610 nm band is found to be associated with a single electron‐accepting site and the 330 nm band is associated with a two electron‐accepting site. Electron paramagnetic resonance analysis during the titration indicates that neither the Type 1 Cu2+(the “blue” Cu2+) nor the Type 2 Cu2+ (the “non‐blue” Cu2+) are associated with the 330 nm band.
Titration of laccase at pH 8.3 with quinol also associates the 330 nm band with a two electron‐accepting site.
Preliminary stopped‐flow kinetic measurements on the absorbance changes at 330 nm and 610 nm are described and the results suggest an involvement of the component responsible for the 330 nm band in the catalytic reaction.
The nature of the component responsible for the 330 nm band is discussed in the light of these results and our previous titration results. The findings are consistent with the 330 nm band being associated with the two additional copper atoms in the molecule and agree with our previous suggestion that these copper atoms exist as an electron‐accepting Cu2+ ‐Cu2+ pair in the oxidized protein.
RNA Metabolism in Mammalian Cells at Elevated Temperature
Authors: Warocquier R. , Scherrer K. 
Published: March 2005

RNA synthesis and metabolism were investigated in Hela cells heated to 42°. At this temperature celluar growth is arrested. After prolongued periods of preheating the initial rate of uridine incorporation into RNA is only slightly affected but no new stable RNA accumulates. After a shift down to 37° the normal pattern of RNA formation resumes.45 S precursor to rRNA is still formed but its normal metabolism to functional rRNA is blocked. No new rRNA appears in cytoplasmic ribosomes. On the contrary, the synthesis of nascent messenger‐like RNA is only slightly affected and non‐ribosomal RNA appears in the cytoplasm at a normal rate. The temperature sensitive event seems thus to be selectively located in the metabolic chain producing functional rRNA.