Tag Archives: inhibition

Influence of organic solvents on the furin activity

T. V. Osadchuk1, O. V. Shybyryn1, A. V. Semyroz1, V. K. Kibirev1,2

1Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kyiv;
2Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: osadchuk@bpci.kiev.ua

Furin belongs to a family of calcium-dependent serine proprotein convertases, which transform the inactive protein precursors into mature polypeptides. In model experiments, we studied the effect of organic solvents such as acetone, dimethyl sulfoxide (DMSO), dioxane, isopropanol and ethanol on the furin activity. Furin was found to retain up to 88% of its initial activity in the presence of DMSO, whereas in the presence of acetone only 30%. Organic solvents formed the following decreasing sequence of their effects on furin: acetone> isopropanol> ethanol> dioxane> dimethyl sulfoxide. The relationship between the residual furin activity and solvent parameters such as relative polarity, dipole moment and log P were investigated. The effect of the organic solvent appeared not to correlate with any of the listed characteristics. Laidler-Sсatchard’s graphs, which according to a theory must be linear, demostrated non-linearity. These results indicate that not only electrostatic interactions play an important role in the studied enzymatic reaction but also other factors, e.g. hydrophobic contacts, hydrogen bonds can influence furin catalysis. This seems relevant for further research in this area.

Influence of cations on furin activity

T. V. Osadchuk1, O. V. Shybyryn1, A. V. Semyroz1,
O. M. Bondarenko1, V. K. Kibirev1,2

1Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: osadchuk@bpci.kiev.ua;
2Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv

Furin is the most studied proprotein convertase which processes inactive protein precursors, converting them into biologically active polypeptides. We have investigated cation effects of cesium, strontium, cadmium, iron, cobalt and nickel on the furin activity. It was shown that in the presence of Ca2+ (1 mM) these ions were able to activate the enzyme, and the peak position of its activity depends on the nature of the ion. Particularly, for Fe2+ it was observed at the ion concentration of 15 mM, whereas for Cd2+, Co2+ and Ni2+ the maximum activity of furin was at 20 mM, for Cs+ the peak was at a concentration of 30 mM, and for strontium ions it was 40 mM. The affinity of the cations for furin was estimated by Lineweaver-Burk plots for low concentrations of ions for the ascending branch of furin activity dependence on the cation concentration. It was found that their affinity in comparison with Ca2+ was sharply reduced (~ 18-150 times). The studied cations (under physiological conditions) were shown not to be able to compete with calcium ions for furin, and in natural environment they cannot influence its activity.

Peculiarities of the influence of сetyltrimethylammonium on the human blood cholinesterases activity

L. P. Kuznetsova, V. A. Samokish, E. E. Sochilina

Sechenov Institute of Evolutionary Physiology and Biochemistry,
Russian Academy of Sciences, St. Petersburg, Russia;
е-mail: esoch@iephb.ru

The influence of cationic detergent cetyltrimethylammonium on the human blood cholinesterases activity (erythrocyte acetylcholinesterase and plasma butyrylcholinesterase) in reactions of hydrolysis of α-thionaphthylacetat and acetylthiocholine is studied. It is shown, that cetyltrimethylammonium is reversible effectоr for both cholinesterases. This compound competitively inhibited enzymatic hydrolysis of acetylthiocholine by both cholinesterases, and in the reactions of enzymatic hydrolysis α-thionaphthylacetat display as the synergistic activator – in experiments with butyrylcholinesterase, and as the reversible inhibitor – in experiments with acetylcholinesterase. Kinetic constants in reaction of acetylcholinesterase inhibition by cetyltrimethylammonium defined by means of different substrates – α-thionaphthylacetat and acetylthiocholin. They are close among themselves and amount (2.5 ± 0.3)×10-5 and (2.8 ± 0.3)×10-5 М, accordingly. Butyrylcholinesterase was more sensitive to influence of cetyltrimethylammonium. The kinetic constants defined for this enzyme by the effect of inhibition of acetylthiocholin hydrolysis or activation of α-thionaphthylatcetat hydrolysis, are also close among themselves and amount (3.9 ± 0.4)×10-6 and (4.4 ± 0.4)×10-6 М, accordin­gly.

Calixarene methylene bisphosphonic acids as promising effectors of biochemical processes

S. V. Komisarenko1, S. O. Kosterin1, E. V. Lugovskoy1, V. I. Kalchenko2

1Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: kinet@biochem.kiev.ua;
2Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kyiv;
e-mail: vik@ioch.kiev.ua

This interdisciplinary study, performed with participation of research workers of Palladin Institute of Biochemistry and Institute of Organic Chemist­ry of NAS of Ukraine, is devoted to analysis of biochemical effects of some calixarene methylene bisphosphonic acids (cyclic phenol oligomers) on two well-known biological phenomenons – Mg2+-dependent ATP hydrolysis (myosin subfragment-1 of myometrium smooth muscle was used as an example) and fibrin polymerization.
Calix[4]arene С-97 (calix[4]arene methylene bisphosphonic acids) is a macrocyclic substance, which contains intramolecular highly ordered lipophilic cavity formed by four aromatic rings, one of which is functionalized at the upper rim with methylene bisphosphonic group. At concentration of 100 µM, this substance was shown to effectively inhibit ATPase activity of pig myometrium myosin subfragment-1 (inhibition coefficient І0.5 = 83 ± 7 µM). At the same time, this calix[4]arene causes significant (vs. control) increase of myosin subfragment-1 hydrodynamic diameter, which may indicate formation of an intermolecular complex between calixa­rene and myosin head. Computer simulation methods (docking and molecular dynamics with addition of grid technologies) enabled to elucidate the grounds of intermolecular interactions between calix[4]arene С-97 and myometrium myosin subfragment-1, that involve hydrophobic, electrostatic and π-π-stacking interactions, some of which are close to the ATPase active centre. In view of the ability of calixarenes to penetrate into the cell and their low toxicity, the results obtained may be used as a basis for further development of a new generation of supramolecular effectors (starting from the above mentioned substances, in particular calix[4]arene С-97) for regulation of smooth muscle contractile activity at the level of ATP dependent actin-myosin interaction.
Calix[4]arenes bearing two or four methylenebisphosphonic acid groups at the macrocyclic upper rim have been studied with respect to their effects on fibrin polymerization. The most potent inhibitor proved to be calix[4]arene tetrakis-methylene-bis-phosphonic acid (C-192), in which case the maximum rate of fibrin polymerization in the fibrinogen + thrombin reaction decreased by 50% at concentrations of 0.52·10-6 M (IC50). At this concentration, the molar ratio of the compound to fibrinogen was 1.7 : 1. For the case of desAB fibrin polymerization, the IC50 was 1.26·10-6 M at a molar ratio of C-192 to fibrin monomer of 4 : 1. Dipropoxycalix[4]-arene bis-methylene-bis-phosphonic acid (C-98) inhibited fibrin desAB polymerization with an IC50 = 1.31·10-4 M. We hypothesized that C-192 blocks fibrin formation by combining with polymerization site ‘A’ (Aa17–19), which ordinarily initiates protofibril formation in a ‘knob-hole’ manner. This suggestion was confirmed by an HPLC assay, which showed a host–guest inclusion complex of C-192 with the synthetic peptide Gly-Pro-Arg-Pro, an analogue of site ‘A’. Further confirmation that the inhibitor was acting at the initial step of the reaction was obtained by electron microscopy, with no evidence of protofibril formation being evident. Calixarene C-192 also doubled both the prothrombin time and the activated partial thromboplastin time in normal human blood plasma at concentrations of 7.13·10-5 and 1.10·10-5 M, respectively. These experiments demonstrate that C-192 is a specific inhibitor of fibrin polymerization and blood coagulation and can be used for the design of a new class of antithrombotic agents.