Energy-conserving reactions in phosphorylating electron-transport particles from Nitrobacter winogradskyi. Activation of nitrite oxidation by the electrical component of the protonmotive force.
(41/124)
1. In electron-transport particles (ET particles) prepared from Nitrobacter winogradskyi, the uncoupling agent carbonyl cyanide phenylhydrazone increased the rate of NADH oxidation but decreased the rate of oxidation of NO2-. Its effectiveness in stimulating NADH oxidation closely paralleled its effectiveness in inhibiting NO2- oxidation. 2. In the presence of ADP and phosphate the oxidation of NADH was stimulated, whereas the oxidation of NO2- was inhibited. In the presence of excess of Pi the concentration dependence with respect to ADP was the same for acceleration of NADH oxidation and inhibition of NO2- oxidation. 3. Oligomycin inhibited NADH oxidation and stimulated the oxidation of NO2-. The concentration of oligomycin required to produce half-maximal effect in both systems was the same. 4. The apparent Km for NO2- was not affected by ADP together with Pi, by uncoupling agent or by oligomycin. 5. With NADH as substrate, classical respiratory control was observed. With NO2- as substrate the respiratory-control ratio was less than unity. 6. A reversible uptake of H+ accompanied the oxidation of NO2- by ET particles. 7. In the presence of NH4Cl or cyclohexylamine hydrochloride, H+ uptake was abolished and increased rates of NO2- oxidation were observed. When valinomycin was present in the reaction medium, low concentrations of NH4Cl inhibited NO2- oxidation. 8. Pretreatment of ET particles with oligomycin enhanced the stimulation of NO2- oxidation induced by NH4Cl or by cyclohexylamine hydrochloride. Pretreatment with the uncoupler carbonyl cyanide phenylhydrazone prevented these stimulations. 9. In the presence of dianemycin together with K+, the uptake of H+ was abolished and the rate of NO2- oxidation was increased. In contrast, in the presence of valinomycin together with K+, the uptake of H+ was increased, and the rate of NO2- oxidation decreased. 10. Sodium tetraphenylboron was found to be an inhibitor of NO2- oxidation, but caused a stimulation of NADH oxidation which was dependent on the presence of NH4Cl or cyclohexylamine hydrochloride. 11. It is concluded that the enhanced rate of NO2- oxidation observed in the absence of energy-dissipating processes clearly relates to some state before the involvement of adenine nucleotides, and it is suggested that the oxidation of NO2- generates a protonmotive force, the electrical component of which controls the rate of NO2- oxidation. (+info)
Reduction of cytochromes by nitrite in electron-transport particles from Nitrobacter winogradskyi: proposal of a mechanism for H+ translocation.
(42/124)
1. A novel component in the respiratory chain of Nitrobacter winogradskyi was identified. This component absorbs maximally at 552.5 nm when in its reduced form, has an Eo' (pH7.0) value of-110mV and undergoes reduction by a mechanism involving the transfer of a single electron. 2. Degrees of reduction of cytochromes c and a1 in electron-transport (ET) particles were monitored during the course of NO2- oxidation, and the effects of ADP together with Pi, oligomycin and of carbonyl cyanide phenylhydrazone were determined. 3. The influences of ionophorous antibiotics, NH4Cl and cyclohexylamine hydrochloride on the reductions of cytochromes c and a1 by NO2- indicate that the flow of reducing equivalents from cytochrome a1 (+350mV) to cytochrome c (+270mV) is facilitated by deltapsi, the electrical component of the protonmotive force. 4. Cytochromes c and a1 in ET particles are reduced by the non-physiological reductant KBH4 in a manner similar to that observed with the physiological reductant NO2-. 5. To account both for the observed cytochrome reductions and for the translocation of H+ ions which accompanies NO2- oxidation, a mechanism is proposed which involves the transfer of a hydride equivalent (H+ plus 2e) inward across the membrane of the ET particle in response to deltapsi. (+info)
Preparation, characterization and in vitro anticancer activity of platinum(II) complexes with N-Cyclohexyl-1,3-propanediamine as the carrier.
(43/124)
New JM118 (active form of satraplatin) analogues with N-cyclohexyl-1,3-propanediamine (N-chpda) as the carrier, cis-[Pt(N-chpda)X2] (X2=2Cl(-) (1), oxalate (2), malonate (3), 1,1-cyclobutanedicarboxylate (CBDCA) (3), and 3-hydroxy-1,1-cyclobutanedicarboxylate(HO-CBDCA) (4)), have been synthesized and characterized by elemental analysis and spectroscopic data along with X-ray crystal structure for a representative compound cis-[Pt(N-chpda)Cl2]. The complexes have also been evaluated for their in vitro anticancer activity. All these analytical data are in good agreement with the structures of the desired compounds. The Pt(II) is in a square planar environment and is coordinated by a chelating N-chpda ligand and 2Cl(-) in cis position, and there are two crystallographically independent cis-[Pt(N-chpda)Cl2] molecules linked together by intermolecular N-H...Cl hydrogen bonds. Compounds 1 and 2 are very active against human lung cancer cell line (AGZY) and human lymphocytic leukemia cell line (Raji), and are much more active than carboplatin. Platinum(II) complexes with N-cyclohexyl-1,3-propanediamine is an alternative choice for mixed ammine/aminoplatinum anticancer drugs. (+info)
Purification and some properties of cyclohexylamine oxidase from a Pseudomonas sp.
(44/124)
Cyclohexylamine oxidase was purified 90-fold from cell-free extracts of Pseudomonas sp. capable of assimilating sodium cyclamate. The purified enzyme was homogeneous in disc electrophoresis, and the molecular weight was found to be approximately 80,000 by gel filtration. The enzyme catalyzed the following reaction: cyclohexylamine+O2+H2O leads to cyclohexanone+NH3+H2O2. The enzyme thus can be classified as an amine oxidase; it utilized oxygen as the ultimate electron acceptor. The pH optimum of the reaction was 6.8 and the apparent Km value for cyclohexylamine was 2.5 X 10(-4) M. The enzyme was highly specific for the deamination of alicyclic primary amines such as cyclohexylamine, but was found to be inactive toward ordinary amines used as substrates for amine oxidases. The enzyme solution was yellow in color and showed a typical flavoprotein spectrum; the addition of cyclohexylamine under anaerobic conditions caused reduction of the flavin in the native enzyme. The flavin of the prosthetic group was identified as FAD by thin layer chromatography. The participation of sulfhydryl groups in the enzymic action was also suggested by the observation that the enzyme activity was inhibited in the presence of PCMB and could be recovered by the addition of glutathione. (+info)
Evidence for allosteric interactions of antagonist binding to the smoothened receptor.
(45/124)
Spermidine regulates insulin synthesis and cytoplasmic Ca(2+) in mouse beta-TC6 insulinoma cells.
(48/124)
In order to assess the functional role of the polyamines spermidine and spermine in pancreatic beta-cells, we examined the effect of spermidine and spermine synthase inhibitors, trans-4-methylcyclohexylamine (MCHA) and N-(3-aminopropyl)cyclohexylamine (APCHA), on cellular polyamine and insulin contents, insulin secretion, and cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) in mouse insulin-secreting Beta-TC6 cells. The cellular spermidine and spermine contents were reduced 90% and 64% by cultivation of cells in the presence of MCHA and APCHA for 3 days, respectively. Addition of spermidine or spermine reversed the polyamine level reduced by MCHA or APCHA, respectively. Insulin secretion was decreased 40~60% in the cells treated with MCHA or APCHA. The reduction by MCHA was reversed to the untreated level by adding spermidine exogenously, while the effect of APCHA was not reversed by treatment with spermine. The cellular insulin content was also reduced by treatment with MCHA but not the expression of insulin 1 and 2 genes, suggesting that spermidine was involved in the translation of insulin mRNAs. The elevation of [Ca(2+)](i), a key event triggering insulin secretion induced by glucose, was reduced in Beta-TC6 cells by MCHA treatment. The spermidine synthase inhibitor also augmented the sustained [Ca(2+)](i) rise induced by carbamylcholine but not by a high concentration of KCl or nicotine. These results suggested that spermidine rather than spermine plays an important role in the regulation of insulin synthesis and the glucose-induced [Ca(2+)](i) rise in Beta-TC6 cells. (+info)