bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adenine Nucleotide Translocation of Mitochondria
Authors: Pfaff E. , Klingenberg M. 
Published: March 2005

The adenine nucleotide translocation in mitochondria has previously been established as an exchange between exogenous and endogenous adenine nucleotides across the inner membrane. The specificity and the control of the exchange are examined with the following major results:

The adenine nucleotide translocation is relatively specific for exogenous ADP and ATP, AMP being nearly inactive. Among other nucleotides tested, only dADP and dATP exchange with a noticeable activity.
In the controlled state ADP exchanges 2–4 times faster than ATP. If simultaneously added, ADP and ATP compete for the exchange, with ADP being about tenfold more active than ATP.
The specificity of the exit of adenine nucleotides in the exchange is similar to the specificity of the entrance with the difference that ADP and ATP are released with equal activity in proportion to their intramitochondrial content. AMP is released only after a slow conversion to ADP. Therefore the short time exchange is limited by the endogenous content of ADP plus ATP.
The exchange is influenced by the metabolic state of the mitochondria. The ATP exchange is more variable than the ADP exchange. Two effects are elucidated: (a) the influence of the metabolic state on the relative content of AMP which inhibits both the ADP and ATP exchange (b) the coupling of the energy transfer system which inhibits only the ATP exchange. An example for case (a) is the inhibition of the ADP and ATP exchange by arsenate and an example for case (b) is the strong increase of the ATP exchange on uncoupling.
The following effects are relevant to the mechanism of the control of the exchange by ATP. The stimulation of the ATP exchange by uncoupler has the same concentration dependence as the uncoupling of oxidative phosphorylation (Km [CCP] = 0.08 μM, where CCP = carbonyl‐cyanide‐phenylhydrazone). Oligomycin does not abolish the uncoupler effect on the ATP exchange. “Endogenous uncoupling” on aging of mitochondria also stimulates the ATP exchange. Valinomycin plus K+ only slightly stimulate the ATP exchange. Anaerobiosis stimulates the ATP exchange to a smaller extent than uncoupling.In competition with ADP the effects of energy transfer on ATP exchange are more strongly revealed. On uncoupling the more than tenfold preference for ADP is fully abolished.
It is concluded that basically the exchange for ADP and ATP has equal specificity in forward and reverse reaction. In the controlled state a superimposed force makes the specificity asymmetric and inhibits the entrance of ATP. This control of the ATP exchange is concluded to be based on the anionic character of the adenine nucleotides. Thus the ATP4‐ex–ADP3‐in exchange is inhibited unless the charge difference is compensated for by an uncoupler stimulated H+ movement across the membrane. Furthermore an electric potential gradient appears to be effective in the controlled state which is abolished on uncoupling.
Interactions entre pigments et acides nucléiques
Authors: Courtois Y. , Guschlbauer W. , Fromageot P. 
Published: March 2005

In this study, several properties of actinomycin D have been examined:

The effect of different solvents upon absorption, optical rotary dispersion and circular dichroism show that the optical activity does not coincide with the absorbance maximum around 440 mμ. Further an association between the polypeptide rings of actinomycin in aqueous solutions is quite possible.
The increase in optical rotatory dispersion when the actinomycin‐DNA complex is formed shows that the molecular asymmetry of the actinomycin molecule is enhanced. This is in contrast to the observations made upon acridine‐DNA complexes where the optical activity decreases with increasing DNA concentration. This clearly shows that the optical activity of the actinomycin‐DNA complex does not result from interactions between dye molecules specifically oriented by the DNA, but by interactions between DNA and the dye. The fixation of actinomycin on helical DNA imposes a highly specific orientation of both the phenoxazine and the two lactone rings, the result of which is the increase of the optical activity of the dye.
The optical rotatory dispersion of the weak actinomycin‐deoxyguanosine complex can clearly be distinguished from the much firmer actinomycin‐DNA complex. The optical rotatory dispersion curve of this complex is different both in amplitude and shape compared with that of the actinomycin‐DNA complex. This is due to the greater sterical freedom which imposes much less constraint to the conformation of the bound actinomycin molecule.
Acid denaturation of the actinomycin‐DNA complex below pH 3 shows the appearance of an association of the type actinomycin‐deoxyguanosine. While it is difficult to separate these changes by absorbance measurements it can unequivocally be distinguished by optical rotatory dispersion.
No complex formation could be detected between actinomycin and polydeoxyguanylic acid.
Structure of Porcine Cholecystokinin‐Pancreozymin
Authors: Mutt V. , Jorpes J. E. 
Published: March 2005

Cholecystokinin‐pancreozymin has been found to have the partial structure Lys (Ala1, Gly1, Pro1, Ser1) · Arg · Val (Ile1, Met1, Ser1) Lys · Asn (Asx1, Glx1, His1, Leu2, Pro1, Ser2) Arg. Ile (Asp1, Ser1) Arg · Asp [Gly1, Met2, Trp1, Tyr (SO3H)] Asp · Phe · NH2.Of the four peptide bonds in this polypeptide, three arginyl and one lysyl, that are cleaved by trypsin only the arginyl‐valine bond is cleaved by thrombin, with retention of the cholecystokinin and pancreozymin activities of the original molecule in the C‐terminal heptacosapeptide. The C‐terminal tryptic octapeptide too has strong cholecystokinin and pancreozymin activity. Except for the replacement of a threonine with methionine the eight amino acid units of this peptide are the same as those that comprise the corresponding part of the molecule of caerulein. Also like that in caerulein, the phenolic group of the only tyrosine of cholecystokinin‐pancreozymin is esterified with sulphuric acid.
Binding of Glycolytic Enzymes to Structure Proteins of the Muscle
Authors: Arnold H. , Pette D. 
Published: March 2005

Only 60–70% of the total activity of aldolase can be extracted from rat or rabbit muscle homogenates with aqueous solutions of relatively low ionic strength. The extraction of aldolase from muscle tissue is only complete in aqueous solutions with an ionic strength greater than 0.2. The fraction of aldolase which is set free at high ionic strength is not located within a special cellular compartment but is present in a bound form and is desorbed in dependence of the ionic strength of the extraction medium.
F‐actin, myosin, acto‐myosin and stroma‐protein were prepared from rabbit muscle and the binding of aldolase to each of these structure proteins was studied in vitro. A completely reversible binding of aldolase to F‐actin, actomyosin, myosin and stroma protein was found. F‐actin possesses by far the highest binding capacity. 100% of the enzyme is bound when 1 mg of aldolase is added to 1 mg of highly purified F‐actin. Under identical experimental conditions acto‐myosin binds 40%, myosin 25%, and stroma protein only 15% of the aldolase activity.
A modified Langmuir isotherm is derived, and the analytical evaluation supports the assumption that the binding of aldolase to F‐actin occurs at two different binding sites.
The binding of aldolase to F‐actin and other structure proteins depends on the ionic strength. At 150 mM KCl, a complete desorption occurs, and 50% of the actin‐bound aldolase is set free at a concentration of 80 mM KCl. The sigmoid shape of the desorption curve indicates a cooperative mechanism of the binding phenomenon.
Within the physiological range, the pH does not influence the binding of aldolase to F‐actin.
Similar to aldolase, glyceraldehydephosphate dehydrogenase is bound to F‐actin, and under the experimental conditions, 1 mg of F‐actin binds up to 1.2 mg of glyceraldehydephosphate dehydrogenase.
Studies with a purified preparation of myogen reveal that also fructose‐6‐phosphate kinase, and in a lower degree phosphoglycerate kinase, pyruvate kinase and lactate dehydrogenase can be adsorbed to F‐actin. No binding occurs in the case of creatine kinase.
The possible significance of the binding phenomenon is discussed with respect to the location of the Embden‐Meyerhof system at the site of the actin filaments within the isotropic zones of the cross‐striated muscle fiber.
Carboxyl‐Terminal Region of Human and Bovine Erythrocyte Carbonic Anhydrases
Authors: Nyman P. O. , Strid L. , Westermark G. 
Published: March 2005

Carboxyl‐terminal sequences have been determined for forms B and C of the human erythrocyte carbonic anhydrase and form B of the bovine enzyme. The proteins were degraded with CNBr, and peptide fragments of 20 residues were isolated from human enzyme C and bovine enzyme B while the human B form gave a fragment consisting of only 19 residues. The sequences of these fragments were determined and by carboxypeptidase digestion of the whole proteins it was shown that they represent the carboxyl‐terminal part of the proteins.
Comparison of the sequences of the enzymes gives strong support for evolutionary homology. Greater similarities in sequence are found between bovine carbonic anhydrase and human carbonic anhydrase C than between the two forms of the human enzyme.
All sequences contain an Arg‐Pro peptide bond. In two of the sequences this bond was found to be hydrolyzable with trypsin.
Formation and Metabolism of Cholest‐5‐ene‐3β,12α‐diol
Authors: Einarsson K. 
Published: March 2005

When labeled cholesterol was incubated with the 20,000 ×g supernatant fluid of rat liver homogenate, cholest‐5‐ene‐3β,12α‐diol could be isolated only in very small amounts indicating that cholest‐5‐ene‐3β,7α‐diol is the predominant intermediate in the conversion of cholesterol into cholest‐5‐ene‐3β,7α,12α‐triol. In the presence of 20,000 ×g supernatant fluid tritium‐labeled cholest‐5‐ene‐3β,12α‐diol was converted into 7α,12α‐dihydroxycholest‐4‐en‐3‐one mainly by means of the intermediary formation of cholest‐5‐ene‐3β,7α,12α‐triol. In the presence of microsomal fraction fortified with NADP, cholest‐5‐ene‐3β,12α‐diol was converted into 12α‐hydroxycholest‐4‐en‐3‐one. Tritium‐labeled 12α‐hydroxycholest‐4‐en‐3‐one was converted in the presence of 100,000 ×g supernatant fluid into 5β‐cholestane‐3α,12α‐diol by means of the intermediary formation of 12α‐hydroxy‐5β‐cholestan‐3‐one. When 12α‐hydroxycholest‐4‐en‐3‐one was incubated with the 20,000 ×g supernatant fluid, small amounts of 5β‐cholestane‐3α,7α,12α‐triol were formed. No 7α‐hydroxylated metabolites could be identified when tritium‐labeled 12α‐hydroxy‐5β‐cholestan‐3‐one and 5β‐cholestane‐3α,12α‐diol were incubated with the 20,000 ×g supernatant fluid.After administration of tritium‐labeled 12α‐hydroxycholest‐4‐en‐3‐one to bile fistula rabbits 2–3% of the bile acids formed consisted of cholic acid. After administration of tritium‐labeled 12α‐hydroxy‐5β‐cholestan‐3‐one and 5β‐cholestane‐3α,12α‐diol no significant amounts of cholic acid could be identified.It is concluded that the initial reaction in the conversion of cholesterol into cholic acid is predominantly a 7α‐hydroxylation.
Ribosome‐Catalyzed Peptidyl Transfer
Authors: Maden B. E. H. , Monro R. E. 
Published: March 2005

Effects of cations and pH value on ribosome‐catalyzed peptidyl transfer were studied, using as assays the reaction of puromycin with (a) washed, polyphenylalanine‐charged Escherichia coli ribosomes and (b) terminal fragments from formlyl‐methionyl‐tRNA (CAACCA‐Met‐F and CCA‐Met‐F) in the presence of purified 50 S ribosomal subunits. In both systems the reaction required the presence of suitable divalent and monovalent cations, and was progressively inhibited below pH 8.5.In the polyphenylalanine system Mg2+ was active over the range 0.3 mM to 1 M, with a broad optimum from approximately 3 to 100 mM. Mg2+ was replaceable by Ca2+ or Mn2+. Other divalent metal ions were inert or inhibitory. Spermidine was also inert. Monovalent cations were active in the order, NH4+ > K+= Rb+ > Cs+. NH4+ and K+ were progressively more effective from 10 mM to at least 1 M. Na+ and Li+ were inert.The reaction of formyl‐methionyl oligonucleotides with puromycin showed similar responses to the polyphenylalanine system except that (a) Mg2+ was active over the range 5 mM to 1 M with an optimum at approximately 100 mM, (b) Ca2+ was inert, (c) K+ was inactive below 100 mM, and (d) NH4+ was only weakly active.The bearing of the results on the mechanism of ribosome‐catalyzed peptidyl transfer is discussed, and a possible application of the results is noted.
Studies on the Metabolism of C19‐Steroids in Rat Liver
Authors: Gustafsson J.‐Å. , Lisboa B. P. , Sjöpvall J. 
Published: March 2005

The formation of androstanetriols after incubation of testosterone with 105,000 ×g microsomes of adult male rat liver was investigated. The steroids were isolated by thin‐layer chromatography and were identified by gas chromatography‐mass spectrometry as 5α‐androstane‐2β,3α,17β‐triol, 5α‐androstane‐3α,7α,17β‐triol and 5α‐androstane‐3α(and 3β),16α,17β‐triol. Incubation of 2β‐ and 7α‐hydroxytestosterone only gave androstanetriols with a 3α‐configuration while incubation with 6β‐ and 16α‐hydroxytestosterone resulted in the formation of both the 3α‐ and 3β‐epimers of the respective androstanetriols. After incubation with 5α‐dihydrotestosterone the following androstanetriols were isolated: 5α‐androstane‐2β,3α(and 3β),17β‐triol, 5α‐androstane‐3α(and 3β),7α,17β‐triol and 5α‐androstane‐3α(and 3β),16α,17β‐triol. No steroid with a 6β‐hydroxy group could be isolated after this incubation. When 5α‐androstane‐3α,17β‐diol was incubated only 5α‐androstane‐2β,3α,17β‐triol was formed, and 5α‐androstane‐3β,17β‐diol was not hydroxylated in the microsomes. These findings indicate a substrate specificity for the 2β‐, 6β‐, 7α‐ and 16α‐hydroxylases.After incubation of testosterone with 105,000 ×g liver microsomes from male germfree rats the same metabolites were isolated as after incubation with microsomes from conventional rats.
Hexopyranoside: Cytochrome c Oxidoreductase from Agrobacterium tumefaciens
Authors: van Beeumen J. , de Ley J. 
Published: March 2005

An inducible enzyme, catalyzing the formation of 3‐ketosugars, has been isolated in a pure state from Agrobacterium tumefaciens, grown on lactose. It occurs in the cytoplasm. It is a FAD‐protein with a sedimentation coefficient of 5.1 S and a molecular weight of 85,000 × 7,700. The pH optimum varies with the nature of the electron acceptor: with cytochrome c it is 7.0, with 2,6‐dichlorophenolindophenol 6.0 and with 5‐methylphenazinium methyl sulphate 7.9. p‐Chloromercuribenzoate, and to some extent atabrine, have an inhibitory effect. In view of its lability, the enzyme is best preserved in a nitrogen atmosphere at pH 7 and 0°. The substrate specificity as studied with a variety of sugars, justifies the name of hexopyranoside: cytochrome c oxidoreductase for the enzyme. As a rule, disaccharides are more easily oxidized than monosaccharides. The highest affinity is observed with cellobiose and lactobionic acid (Km=2.0 × 10‐4M). Most of the 3‐ulose endproducts were detected by thin layer and/or polarography. The minimal structural requirements of a substrate sugar allow the proposal of a molecular model for the active centre of the enzyme.The oxidation‐reduction potential at pH 7 and 25° of the system lactose/3‐ketolactose is calculated to be Eo=+0.16 V.
Proteine aus Neurospora crassa
Authors: Friemel H. , Peseke H. , Kleist H. , Brock J. , Bienengräber V. , Mücke D. 
Published: March 2005

The mycelium of Neurospora crassa was cultivated in a minimal liquid medium in surface culture. The moist mycelium was lyophilized, powdered, and eluted using 0,14 M sodium chloride solution for extracting the proteins. The enrichment of these proteins was carried out by means of ultrafiltration (vacuum and pressure filtration). The extracted proteins of N. crassa were characterized by paper‐, agar gel‐ and immuno‐electrophoresis. The antisera were obtained by immunising rabbits for 21 weeks.By means of agar gel electrophoresis 5 zones of proteins were separated in N. crassa 3a6A; by means of immunoelectrophoresis 17 bands resulted from the same protein mixture. The electrophoretic mobilities of the precipitation arcs were calculated. The immunoelectrophoretic patterns of N. crassa E 5256 obtained by N. crassa 3a6A antiserum nearly agreed with the bands of N. crassa 3a6A antigen. However there were no corresponding results in the patterns obtained from N. crassa 46001–1–1a and N. crassa 6994a with the same antiserum. It may be assumed that these differences depend on the different genetic enzyme patterns of the wild and mutant strains; they are also responsible for the differences in the rates of synthesis depending on the duration of cultivation.
Proteine aus Neurospora crassa.
Authors: Bienengräber V. , Friemel H. , Brock J. , Kleist H. , Mücke D. 
Published: March 2005

In additional experiments on characterizing cytoplasmic proteins in Neurospora crassa (N. crassa) the enzyme and isoenzyme patterns of this fungus were analyzed. By agar gel electrophoresis the following isoenzymes were found in several N. crassa strains: 5 isoenzymes of Lactate dehydrogenase, 5 isoenzymes of Glycerolphosphate dehydrogenase, 5 isoenzymes of Glutamate dehydrogenase and 3 isoenzymes of Malate dehydrogenase. Carboxylesterase was separated into 4 fractions by means of agar gel electrophoresis.By immunoelectrophoresis some precipitation arcs proved to be carrying enzymatic activities. Depending on the tested N. crassa strain the activity of Carboxylesterase could be localized in 2–4 precipitation arcs. ρ‐Diphenoloxidase was found as an elongated precipitation line by means of immunoelectrophoresis. Ribonuclease was seen in 2 precipitation arcs on the anodic and cathodic side of the starting point. 2 isoenzymes of Peroxidase were demonstrated in N. crassa 3a6A. One precipitation arc near the starting point indicated the activity of Catalase.
Enzymic Flux Rates in vivo through the Embden‐Meyerhof Pathway and the Nucleotides of the Mouse Liver
Authors: Reich J. G. , Till U. , Günther J. , Zahn D. , Tschisgale M. , Frunder H. 
Published: March 2005

The enzymic flux rates through the Embden‐Meyerhof pathway and the nucleotides of the liver have been measured in vivo with the [32P]Pi‐tracer technique. The specific radioactivities of 15 positions in 11 metabolites have been measured within the first minute after injection of carrier‐free [32P]Pi. The results have been treated with the analogue computer technique. The main conclusions are:

The turnover of all liver compounds examined is in the range of from seconds to minutes. The velocity of oxidative phosphorylation is so high that within 30 sec after the tracer injection prestationary kinetics is observed, indicating that the turnover of the γ‐P position of ATP amounts to more than 25 μmoles per g fresh liver per min.
The labelling of ATP‐γ‐P is rapidly redistributed within the other nucleotide β‐ and γ‐P‐positions, the reactions of the nucleoside diphosphokinase type being more rapid than with the monophosphokinase type.
The rate of net glycolysis or gluconeogenesis is less than 0.1 μmoles per g per min in the postabsorptive state.Synthesis of glycogen or UDP‐glucuronic acid via UDPG is less than 0.3 μmoles per g per min.The absolute turnover rate of glucose 6‐phosphate is about 3 μmoles per g per min.The pathway of glucose 6‐phosphate formation and the fate of glucose 6‐phosphate cannot be measured on the basis of 32P‐experiments alone.
Phosphofructokinase as well as aldolase and fructose 1,6‐biphosphate phosphohydrolase are inhibited in vivo. In the latter two cases, adequate kinetic explanation of this phenomenon is not available from in vitro results of the literature.The isotope flux via glucosephosphate isomerase amounts to 0.4 μmoles per g per min. This is about one order of magnitude smaller than expected from the maximal activity and from the kinetic behaviour of the enzyme in vitro.
Synthesis of about 0.7 μmoles of glycerol 3‐phosphate from ATP and glycerol takes place per g per min. At least 0.7 μmoles of phosphoenolpyruvate are synthesized per g per min without being converted to fructose 1,6‐biphosphate. The fate of phosphoenolpyruvate is unknown. Reconversion to pyruvate or conversion to lipid glycerol is possible.
Analogue Computer Analysis of Tracer Flow Patterns through the Glycolytic and Related Pathway in Erythrocytes and other Intact Metabolic Systems
Authors: Reich J. G. 
Published: March 2005

The technique and theoretical implications of an analogue computer processing of tracer data in complex metabolic systems are outlined. The procedure may be used for the prediction and analysis of experimental results. The analysis is carried out in three steps: model construction and mathematical formulation; construction of one particular set of fluxes compatible with the data; generalization to give all compatible flux combinations and to fix restrictions on permissible flux values.Usually, metabolic systems are characterized by a slow input of radioactivity. The resulting numerically ill‐conditioned matrices either restrict the extractibility of certain parameters or lead to ambiguous results. Uses and limitations of the procedure are discussed in terms of glycolytic net flow in erythrocytes. In contrast to intuitive conclusions in previous papers, a detailed treatment of the literature data reveals that some 50% of the net flow goes via the biphospho‐glycerate shunt. Usually, tracer experiments yield the isotopic shuttle rather than the net flux rate. However, an expression of the shuttle in terms of the free enthalpy or the equilibrium of the reaction may be derived. Thus, absolute flow and net flow are of similar information content for regulation problems. The applicability of free‐energy considerations in vivo may be tested directly with the tracer method.
Zur Biosynthese der Apiose
Authors: Sandermann H. , Grisebach H. 
Published: March 2005

The ethanolic extract of 8‐week‐old parsley plants was chromatographed on Dowex‐1×2 with a concave gradient using the buffer system of Hurlbert. After further purification on carboncelite columns, paper chromatography and high‐voltage electrophoresis, 120 μmoles of a homogeneous UDP‐sugar fraction were obtained. The sugars present in this fraction were identified after acid or enzymatic hydrolysis (Crotalus adamanteus venom, acid phosphatase) by various chemical and enzymatic tests. A modified Dische test which is specific for apiose and a quantitative determination of d‐xylose with d‐glucose–oxidase were developed.According to the analytical investigations the UDP‐sugar fraction had the following composition (μmol): UDP‐d‐glucose (84), UDP‐d‐galactose (27), UDP‐d‐xylose (4), UDP‐l‐arabinose (2), UDP‐fructose (0.42), UDP‐l‐rhamnose (2.4), and UDP‐apiose (0.18). The presence of UDP‐apiose in parsley strongly corroborates the proposed biosynthetic pathway for the formation of d‐apiose via UDP‐d‐glucuronic acid.