Thermodynamics of fatty acid degradation.

In this communication, the correlation of some thermodynamic properties of structurally similar biological compounds with items such as the number of carbon atoms or the number of its characteristic groups, such as phosphates, was applied to enzyme thermodynamics, to advance the thermodynamics of fatty acid degradation. It was shown that these concepts apply equally well for all three major thermodynamic functions: Gibbs energy of formation, enthalpy of formation, and entropy of formation. First, the standard transformed Gibbs energies of formation, Δ(f)G'(o), were calculated for the major portion of saturated fatty acids at 25 °C and pH 5, pH 7, and pH 9.

Optimization of conditions for acid protease partitioning and purification in aqueous two-phase systems using response surface methodology.

Aspergillopepsin I, an acid protease, was purified using an aqueous two-phase system that comprised various combinations of polyethylene glycol (PEG), NaH2PO4 and NaCl. Partition of the enzyme depended upon the molecular mass of the PEG and the presence of NaCl. With PEG 1500, 4000 and 6000, the partition coefficients were increased by 1,500-, 1,800- and 560-fold compared to values without NaCl.

Deriving the rate equations for product inhibition patterns in bisubstrate enzyme reactions.

In this work, the full rate equations for 17 completely reversible bisubstrate enzyme kinetic mechanisms, with two substrates in the forward and two in the reverse direction, have been presented; among these are rapid equilibrium, steady-state, and mixed steady-state and rapid equilibrium mechanisms. From each rate equation eight product inhibition equations were derived, four for the forward and four for the reverse direction. All the corresponding product inhibition equations were derived in full; thus a total of 17 x 8 = 136 equations, were presented.

Glucose oxidase from Aspergillus niger: the mechanism of action with molecular oxygen, quinones, and one-electron acceptors.

Glucose oxidase from the mold Aspergillus niger (EC 1.1.3.

Inactivation of cytochrome-c with glucose oxidase.

A novel reaction of cytochrome-c from the horse heart with the enzyme glucose oxidase from Aspergillus niger (EC 1.1.3.

The chemical mechanism of action of glucose oxidase from Aspergillus niger.

Glucose oxidase from Aspergillus niger (EC 1.1.3.

A general method for the analysis of random bisubstrate enzyme mechanisms.

In the present communication, a general method for the kinetic analysis of random bisubstrate mechanisms is described. The method comprises a stepwise application of the following kinetic and ligand-binding experiments: determination of steady-state kinetic constants, product inhibition patterns, maximum rate relationships, application of alternate substrates, application of dead-end inhibitors, direct binding of substrates, kinetic isotope effects, and isotope exchange studies. This general method was applied to a practical example: a yeast alcohol dehydrogenase-catalyzed oxidation of 2-propanol by NAD(+) at pH 7.

The three zinc-containing alcohol dehydrogenases from baker's yeast, Saccharomyces cerevisiae.

This review is a summary of our current knowledge of the structure, function and mechanism of action of the three zinc-containing alcohol dehydrogenases, YADH-1, YADH-2 and YADH-3, in baker's yeast, Saccharomyces cerevisiae. The opening section deals with the substrate specificity of the enzymes, covering the steady-state kinetic data for its most known substrates. In the following sections, the kinetic mechanism for this enzyme is reported, along with the values of all rate constants in the mechanism.

Cultivation of Polyporus squamosus for pectinase production in aqueous two-phase system containing sugar beet extraction waste.

Cultivation of the fungus Polyporus squamosus for pectinase production was studied in a polyethylene glycol/crude dextran aqueous two-phase system, with sugar beet extraction waste as pectin source. Fungal growth was restricted to the bottom phase and the amounts of biomass and exo-pectinase activity produced were superior to in homogeneous cultivation. The partition coefficients of endo-pectinase and exo-pectinase were 4.

Production of pectinases by Polyporus squamosus in aqueous two-phase system.

The ability of Polyporus squamosus to grow and produce pectinases in an aqueous two-phase medium composed of polyethylene glycol and crude dextran is reported. Fungal growth was restricted to the bottom phase leaving the top phase cell free. Amounts of produced biomass and endo and exo-pectinase activities were superior or equal to those obtained in homogeneous medium.

Production and some characteristics of beta-glucosidase in Diaporthe (Phomopsis) helianthi.

Diaporthe (Phomopsis) helianthi Munt.-Cvet. et al.

Inhibition by isoproterenol of the passive potassium efflux from pigeon erythrocytes.

Pigeon erythrocytes were carefully washed in an isotonic neutral buffer, devoid of potassium, and the rate of passive unidirectional efflux of potassium from the cells into a K+-free medium was measured after 20 min, at 40 degrees C. Isoproterenol inhibits K+-efflux by 35-45%, at a cell concentration of 1%; the isoproterenol effect is mediated by beta-adrenergic receptors. Cyclic AMP mimics the effect of isoproterenol, but at 4-5 orders of magnitude higher concentrations.

The influence of nicergoline on reaction kinetics of various forms of cyclic AMP phosphodiesterase.

10-Methoxy-1,6-dimethylergoline-8 beta-methanol-5-bromonicotinate (nicergoline) has in vitro a modulatory effect upon reaction kinetics of various forms of cAMP phosphodiesterase (PDE) from beef heart and mice brain. Nicergoline inhibits low Km form of cAMP PDE from hear and brain; concentration of inhibitor required for 50% inhibition is 3-12 mumol/l. It is believe that the observed in vitro effects of nicergoline on reaction kinetics of various forms of cAMP PDE may in vivo help to normalize the level of cAMP, keep its concentration within certain limits, both by opposing large increase and large decrease in its cellular concentration.

The influence of nicergoline on reaction kinetics of synaptosomal adenosine triphosphatases from porcine brain.

10-Methoxy-1,6-dimethylergoline-8beta-methanol-5-bromonicotinate (nicergoline) has in vitro a modulatory effect upon reaction kinetics of two synaptosomal adenosine triphosphatases from porcine brain: Na,K-dependent ATPase and Ca,Mg-dependent ATPase. Nicergoline is a non-competitive inhibitor of synaptosomal Ca,Mg-dependent ATPase in vitro; thus, if its in vivo concentration reaches a sufficiently high level, the rate of exchange of Ca and Mg ions between the intra- and the extracellular spaces of neurons slows down. In vivo effect of nicergoline upon reaction kinetics of synaptosomal Na,K-dependent ATPase is complex; below 80 micromol/l ATP it is an activator, and above 80 micromol/l ATP it is an inhibitor or enzyme.

Influence of temperature on hemolysis of erythrocytes by digitonin.

The kinetics of hemolysis of pig erythrocytes by digitonin was continuously monitored by a potassium selective electrode. The following minimal mechanism of hemolysis was postulated, based upon kinetic measurements: 2 D + E (1)in equilibrium E x D2 (2)leads to (E x D2) (3)leads to (E x D2) where D denotes a digitonin molecule and E a specific digitonin binding-site on the membrane. The first step (1) represents a rapid reversible combining of digitonin with specific binding-sites on the membrane.