Tag Archives: enzymatic hydrolysis

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.

Kinetics of hydrolysis of 1,4-benzodiazepine derivative by carboxylesterases in mice organism

M. Ya. Golovenko, V. B. Larionov

A. V. Bogatsky Physics-Chemical Institute, National Academy of Sciences of Ukraine, Odesa;
e-mail: lvb_78@mail.ru

Chemical modification of the physiologically active substances and creation of prodrugs is one of the ways for pharmacotherapy optimization. The aim of the work was determination of the kinetic parameters of nonspecific esterases that catalyze hydrolysis of new hypnotic drug Levana (1,4-benzodiazepine derivative). The experiments were carried out using the 14C-labelled Levana and its active metabolite – 3-hydrixyphenazepam. In vitro it was shown that Levana undergoes spontaneous hydrolysis even in buffer solution (pH 7.4), though in plasma and homogenates of brain and liver this process is more intensive (conventional Vmax was 6.9 ± 0.5, 19 ± 4 and 12 ± 1 mM/(h∙mg of protein, correspondingly). The samples mentioned differ by activity of tissue estera­ses being most active in the liver (conventional Km 0.45 ± 0.04 mM for the liver and 47 ± 11 mM for the brain). In plasma carboxylesterase activity (for Leva­na) is the lowest (conventional Km 129 ± 10 mM). In vivo it was shown that Levana more easily permeates brain-blood barrier (compared to 3-hydroxyphenaze­pam), that leads to higher concentrations (after hyd­rolysis) of its metabolite in brain tissue. Also it is quantitatively estimated as the increase of concentration (brain/blood) ratio  ~1.4 times.