Addition Of Arsenate Research Articles

Control of pyruvate phosphoroclastic activity in extracts of Clostridium pasteurianum by ADP and acetyl phosphate

1. 1. The ATP requirement for the pyruvate phosphoroclastic reaction has been investigates in extracts of Clostridium pasteurianum, particularly with regard to control of the system. 2. 2. S-Adenosylmethione is not the active component in the ATP requirement in pyruvate metabolism in C. pasteurianum although it is known to be in Escherichia coli and Streptococcus faecalis. 3. 3. AMP and ADP can replace ATP, since enzymes in the extract establish an equilibrium mixture of the three. The active species has been shown to b ADP. 4. 4. Acetyl phosphate is a product inhibitor of the reaction. ADP, through its involvement in the acetate kinase (ATP: acetate phosphotransferase, EC 2.7.4.3) reaction, appears to exert its effect by influencing acetyl phosphate concentration. 5. 5. Arsenate removes the requirement for adenosine phosphate by preventing the accumulation of acetyl phosphate. 6. 6. Pyruvate consumption by extracts of ammonia-grown cells is not stimulated by the addition of ATP. Addition of arsenate, or ATP + ATPase (ATP phosphohydrolase, EC 3.6.1.4), stimulates pyruvate breakdown by preventing the accumulation of acetyl phosphate which otherwise occurs. 7. 7. Increasing ADP concentration counters some of the inhibitory effect of acetyl phosphate, indicating a direct control by ADP in addition to its involvement in acetyl phosphate breakdown. 8. 8. A scheme for the control of pyruvate phosphoroclastic activity in C. pasteurianum is proposed: acetyl phosphate acts as a coarse control and ADP as a fine regulator.

A Study of the Reaction of Glyceraldehyde with Glyceraldehyde 3-Phosphate Dehydrogenase

Abstract Kinetic data indicate that rabbit muscle glyceraldehyde 3-phosphate dehydrogenase possesses two types of diphosphopyridine nucleotide-binding sites. The actual chemical reaction (oxidation-reduction) occurs at tight sites. Binding of DPN to loose sites activates the reaction at the tight sites. These results are consistent with the concept that the enzyme is double headed, with oxidation-reduction heads (which contain the tight sites) and transfer heads (which contain the loose sites). Light scattering data are consistent with the concept that (in the absence of arsenate or phosphate) the enzyme can exist as a dimer (with an apparent weight average molecular weight of 2.8 x 105) which can dissociate upon dilution into monomers (with molecular weights of 1.4 x 105). Dimerization is inhibited by high concentrations of arsenate (0.05 m). This inhibition is overcome by adding DPN to the loose sites. The monomer is unreactive in the absence of arsenate and is markedly activated by adding DPN to the loose sites. The dimer is reactive in the absence of arsenate and is only slightly activated by adding DPN to the loose sites. A kinetic mechanism is proposed which agrees with these and most other observations. This mechanism is sequential with the addition of DPN and then the aldehyde to the oxidation-reduction head. This is followed by the addition of arsenate and then DPN to the transfer head. The mech anism of the reaction with glyceraldehyde and glyceraldehyde 3-phosphate seems to be the same.

The sites of action of atractyloside and oligomycin in the mitochondrial energy-transfer system

1. 1. The respiration of liver mitochondria stimulated by the addition of arsenate was inhibited by oligomycin and not by atractyloside. Aslo the oxidation of the mitochondrial pyridine nucleotide induced by arsenate was inhibited by oligomycin and not by atractyloside. 2. 2. At low arsenate concentrations atractyloside caused a stimulation of the respiration, probably by interfering with the liberation of endogenous inorganic phosphate. 3. 3. The respiration of phosphate-aged mitochondria was also inhibited by oligomycin and not by atractyloside. 4. 4. The synthesis of ATP from substrate-level phosphorylation occuring during the anaerobic dismutation of α-ketoglutarate and ammonia to succinate, CO 2 and glutamate, was inhibited by atractyloside and not by oligomycin. 5. 5. It is concluded that oligomycin inhibits the formation of phosphorylated or arsenylated compounds at the level of the respiratory chain, whereas atractyloside inhibits the formation of external ATP from phosphorylated compounds formed both at the level of the respiratory chain and at the substrate-level phosphorylation.

Biochemical properties of skeletal muscle mitochondria: II. The ATPase activity and the albumin effect

The ATPase activity of freshly prepared pigeon muscle mitochondria is strongly stimulated by addition of Mg 2+ ions. This property is not peculiar to pigeon breast mitochondria, since muscle mitochondria prepared from hearl and skeletal muscles, whether from rat or pigeon, show a similar behavior. The mitochondrial ATPase of rat or pigeon liver mitochondria is not stimulated by Mg 2+. The pH activity curves for ATP hydrolysis indicate that the mitochondria prepared from liver, heart, and skeletal muscle of rat are strongly stimulated by addition of DNP both in presence and in absence of Mg 2+. In contrast the stimulating effect of DNP on mitochondria prepared from liver, heart, and breast of pigeons, is very small and not evident on the acid region of the curve. Bovine plasma albumin added to the medium does not change the oxidation rate of pigeon breast mitochondria, while it strongly increases the phosphorylation capacity and therefore the P O ratio. This effect is associated with an activation of the DNP-stimulated ATPase, particularly between pH 7.5 and 8.5. The effect of albumin on the DNP-stimulated ATPase is shown by all the muscle mitochondria examined and also by those of pigeon liver. Differently from DNP, addition of arsenate to pigeon breast mitochondria strongly stimulates the ATPase activity, whereas the P O ratio is only slightly affected.

Über die Wirkung von Arsenat auf Nitratreduktion, Atmung und Photosynthese von Grünalgen

The effect of sodium arsenate on the metabolism of the green alga,Ankistrodesmus braunii (strain Marburg) increases with increasing arsenate concentration and with decreasing phosphate concentration. Above 10−4 M arsenate, in a phosphate-free medium of pH 4.1, an increase in respiratory oxygen uptake and inhibition of photosynthesis were observed. At the highest concentration used (5·10−2 M arsenate), the rate of respiration was about 250% of that of the controls, whereas photosynthesis had dropped to about 20% of the normal value. In addition, arsenate was found to be an inhibitor of the reduction of nitrite in the dark, whereas it does not inhibit the first step of nitrate reduction,i.e. the reaction nitrate → nitrite. Therefore, in a solution containing nitrate, addition of arsenate leads to accumulation of nitrite. These results further support the assumption, derived previously from experiments with 2,4-dinitrophenol, that the further reduction of nitrite requires high-energy phosphate, in contrast to the first step of nitrate reduction.

Arsenolysis and Phosphorolysis of the Amylose and Amylopectin Fractions of Starch

Doudoroff, Barker and Hassid1 showed that the addition of arsenate to sucrose phosphorylase from Pseudomonas saccharophila catalyses the decomposition of sucrose to glucose and fructose, the reaction being :

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