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A single procedure for the preparation of lactate dehydrogenase (EC 1.1.1.27), the mitochondrial and cytoplasmic forms of malate dehydrogenase (EC 1.1.1.37), adenylate kinase (EC 2.7.4.3) and pyruvate kinase (EC 2.7.1.40) from pig heart is described. The five enzymes are obtained in preparative amounts in homogenous form with specific activities equal to or higher than those pre viously reported. Some molecular properties of pig heart pyruvate kinase are determined.
The NAD analogue [3-(3-acetylpyridinio)-propyl] adenosine pyrophosphate forms enzymically inactive complexes with glyceraldehyde-3-phosphate dehydrogenase from yeast and rabbit skeletal muscle. In the latter enzyme four mol of the analogue are bound with equal affinity inhibiting the enzyme in a competitive way: KI = 0.3 mM as compared to the dissociation constant KD=O.6 mм.
The brominated derivative [3- (3-bromoacetylpyridinio) -propyl] adenosine pyrophosphate is covalently bound to both enzymes causing irreversible loss of enzymic activity. Complete inactivation of the enzyme from muscle requires two moles of the analogue per mol of tetramer. The remaining two sites are still able to bind two mol of NAD+ without regain of enzymic activity. In the case of the yeast enzyme four mol of the analogue are bound. Inactivation of the rabbit muscle enzyme is accompanied by the disappearance of two out of four highly reactive sulfhydryl groups; in the yeast enzyme the four active site cysteine residues are still able to react with DTNB1 the reactivity being diminished significantly.
Hybrid formation between the native enzymes from yeast and skeletal muscle is not affected by the modification of the enzyme. Similarly the sedimentation properties of the covalently modified enzyme are indistinguishable from those of the native molecule. This indicates that both the native and the irreversibly inhibited enzyme are identical regarding their quaternary structure.
Testosterone degrading enzymes are synthesized de novo by bacterium P. testosteroni to utilize testosterone-like steroids as the only source of carbon. RNA-synthesis of the whole lysate of testosterone-induced bacteria was found to be 15% reduced compared to the control, suggesting a cytoplasmatic factor which modulates chromatin associated RNA-polymerase activity.
[ω- (3-Acetylpyridinio) -n-alkyl] adenosine pyrophosphates are coenzyme analogs of NAD⊕. The adenosine pyrophosphate moiety and the 3-acetylpyridine ring of the analogs are connected by n-alkyl chains of different lengths (ethyl -hexyl). The analogs form strong dissociating complexes with lactate dehydrogenase. The complex formation is predominantly achieved by interaction of the ADP moiety with its respective binding domain at the active site.
The redox potentials of the analogs and NAD are of similar magnitude. The coenzyme function of the analogs depends upon the length of the hydrocarbon chain. Lactate dehydrogenase and alcohol dehydrogenases from yeast and horse liver do not catalize hydrogen transfer from their substrates to any other alkyl analog but [4- (3-acetylpyridinio)-n-butyl] adenosine pyrophosphate, aldehyde dehydrogenase from horse liver catalizes hydrogen transfer from acetaldehyde to the pentyl derivative and glyceraldehyde-3-phosphate dehydrogenase catalizes hydrogen transfer to both analogs. In no case, hydrogen transfer from or to one of the 3-acetylpyridine-n-alkyl analogs proceeded with a velocity comparable to NAD or its 3-acetylpyridine analog. The results show that the nicotinamide bound ribose in NAD is involved in the binding and the activation of the coenzyme.
With new X-ray data from a crystal of stoichiometric K0.33MoO3 the crystal structure of this compound was refined until R(anisotropic) = 0.023. The characteristic distortion of the Mo-O octahedra is discussed.
As[N(CH3)2]3 reacts with the following isocyanates: FSO2NCO, n-C4F9SO2NCO, SO2(NCO)2 and (CH3)3SiNCO. The products which result from reaction of FSO2NCO and n-C4F9SO2NCO are the acyclic tri- and bisubstituted arsines [xxx]
In contrast, SO2(NCO)2 and (CH3)3SiNCO form eight- and four-membered ring compounds, where the skeleton consists of the atoms As2S2N4 (3) and As2N2 (4). The new compounds were characterized by NMR and mass spectra.
Über das Verhalten von silicium- und zinnorganischen Verbindungen bei der Synthese von Heterocyclen
(1977)
The isocyanates of silicon (CH3)2Si(NCO)2 and Si(NCO)4 react with CH3N[Sn(CH3)3]2 and N[Sn(CH3)3]3 to yield the cyclic derivatives 2a-2b as well as the spiro compound 3. The structures of the compounds are discussed on the basis of 1H NMR and IR data. Mass spectra are not conclusive for assigning a certain structure. SO2(NCO)2 and (CH3)3Si-S-Si(CH3)3 form a cyclic compound 4 which contains two sulfur atoms of coordination number two and four. The results of the mass spectra can be interpreted by assuming that a rearrangement occurred. 4 hydrolyses under formation of 5.
CH3P(S)(NCO)2 reacts with [(CH3)3Si]2N-CH3, [(CH3)3SiNCH3]2CO and [(CH3)3Sn]3N to give the cyclic compounds 2a-2c. The structures are discussed on the basis of NMR and IR data. In 2 a and 2 b the (CH3)3Si-groups are easily and quantitatively replaced by protons with water under formation of (CH3)3Si-O-Si(CH3)3. By the reaction of CH3P(S)(NCO)2 with [(CH3)3Si]2S 4 is obtained, a cyclic compound with a sulfur atom of coordination number 2.
FP(S)(NCS)2 was used to investigate the scope of these reactions. With [(CH3)3Si]2NCH3 and FP(S)(NCS)2 5 is obtained, which reacts with S2Cl2 to yield 6, a bridged disulfur compound. This method may be useful for the systematic investigation of new cyclic compounds.
Phasentrennung als Folge der Konkurrenz zwischen "statistischer" und "chemischer" Vermischung
(1977)
The fact that common thermodynamic conditions are valid for all known types of critical phases (liquid-liquid, liquid-gas, and "gas-gas") suggests that a common principle for the interpretation of material phase instability from a molecular point of view must exist. In this paper we show that the principle of competition between "statistical mixing" (i. e. random mixing) and "chemical mixing" (i. e. mixing effected under the influence of chemical interactions) can give this common inter pretation. If the equilibrium states resulting from both types of mixing are sufficiently different, phase separation occurs. We refer to our earlier papers (since 1972) in which we have applied this principle to describe liquid-liquid phase equilibria by "chemical" models, using the equilibrium constants of exchange equilibria between nearest-neighbour complexes as a measure of "chemical" mixing. In this paper we show that the well-known reduced gas-liquid coexistence curve, T/Tc =f(q/qc), can accurately be fitted by a very simple "mixture" model of molecules A with "vacan cies", provided that the contributions of both statistical and chemical mixing are incorporated into the formula for GE. From a discussion of the application to "gas-gas" phase equilibria in the hyper critical region it results that the weight factor r, by which the contribution of statistical mixing enters into GE, must depend on the density of the gas mixture. Phase separation can only occur if, by increasing pressure, the contributions to GE of statistical and chemical mixing have reached the same order of magnitude. From an attempt to apply the same principle to solid-liquid equilibria it is shown under which external conditions a critical point for this type of phase transition can be expected.
As we have shown in a recent paper, the principle of competition between "statistical" and "chemical" mixing represents a molecular thermodynamic approach to all known types of phase separation. This principle is effective if the contributions of two independent spontaneous processes enter into the thermodynamic potential by which the resulting equilibrium state of the system is determined. This is equivalent with the statement that two different forms of entropy exist which are not interchangeable, and for which the law of increasing entropy independently must be valid. As "cooperativity" is introduced by this principle, critical phenomena may be described by simple equilibrium models in which only nearest-neighbour interactions are considered.
Starting from the molar Gibbs free energy GM of the most simple binary equilibrium model z = 1 with nearest-neighbour pairs, nonclassical critical-point exponents α = 0.33 of the molar heat capacity, β = 0.33 of the coexistence curve, γ = 1.33 of the isothermal compressibility, and δ = 4.33 of the critical isotherm, are derived, which are consistent with the well-known exponent in equalities. These non-classical critical-point exponents are independent of the chemical nature of the particles because they are obtained by applying thermodynamic arguments on the coupling constant τ, by which the contribution of "statistical mixing" to GM is weighted.