Voprosy meditsinskoi khimii最新文献

The antiproliferative, differentiating and apoptogenic effects of purinic (cytidine and thymidine) and pyrimidinic (guanosine) nucleosides on K562 cells were investigated. Induction of erythroid differentiation (haemoglobin synthesis) in cancer cells was observed after 2 and 4 days incubation with 2 mM thymidine and 1 mM guanosine. Increase of haemoglobin synthesis in K 562 cells incubated with 2 mM cytidine was detected at 4 day. Analysis of the DNA-degrading effect (induction of apoptosis) of the reagents used on K 562 cells by fluorescent dyes and modulation activity of caspase 9 and also caspases 3,7,10 is induced with thymidine and guanosine but not with cytidine.

The full length enteropeptidase or it's light chain have often used for the limited proteolysis of recombinant chimeric proteins incorporating the linker-(Asp)4Lys- to obtain the target protein. Any chimeric proteins were not cleaved by the full length enteropeptidase efficiently. The resistant to the hydrolysis chimeric protein IFN-(Asp)4Lys-HIV earlier was shown to be the competitive inhibitor (Ki = 3,4 x 10(-6) M) in relation to the low molecular substrate. In present study we were determined this chimeric protein competitive inhibited the same substrate hydrolysis by enteropeptidase light chain (Ki = 2,7 x 10(-5) M). Comparison the Ki values for the substrate hydrolysis by full length enzyme and its light chain suggests that the enteropeptidase heavy chain may participate in chimeric protein binding.

The stability of polyacrylamide hydrogel, modified by ovomucoid with immobilized insulin was studied at different pH of external medium. At 3.8 < pH < 5.5 insulin binds to the gel, due to electrostatic interaction between ovomucoid and insulin molecules.

The thermostable endogenous cysteine proteinase inhibitors (CPI) from the primary (REF), immortal (clone IE5) and transformed (clones trF8 and trF8nmcc) fibroblasts were isolated. All the isolated CPI act as reversible competitive inhibitors of cathepsins B and L and of papain. The study of inhibition of cathepsins B and L, purified from the same cell cultures as the CPI, showed that the Ki values for CPI from the cultures of immortal and transformed cells were by one order higher than the Ki values for CPI of primary fibroblasts. The data obtained suggest that immortalization and transformation alter the CPI properties.

The data on biochemical and molecular-genetic diagnostics of a hereditary lisosomal storage disease, late infantile neuronal ceroid lipofuscinosis (CLN2) are presented. The disease is associated with a hereditary deficiency of pepstatin-unsensitive peptidase--tripeptidylpeptidase 1 (TPP1)--caused by mutations in the TPP1-coding gene CLN2. Among the 30 patients with clinical manifestations of CLN, six patients with a pronounced decrease in TPP1 activity were revealed; these data were interpreted as indicating the presence of CLN2 in these patients. The analysis of the isolated DNA indicated the availability of the most widespread mutation g3670 C > T(R208X) leading to the untimely termination of TPP1 synthesis. It was shown that in 5 patients this mutation is present in homozygous state and in one patient, in the heterozygous state. In this patient a hitherto unknown mutation, g3665G > A (R206H), was revealed. The pathogenetic significance of this mutation and the importance of molecular-genetic diagnosis of CLN are discussed with regard to medico-genetic consulting and prenatal diagnosis of this disease.

Enteropeptidase (enterokinase) (EC 3.4.21.9), a highly specific processing protease, initiating a cascade of reactions activating the digestion enzymes. Catalyzing trypsinogen activation enteropeptidase exhibits unique properties for high efficiency hydrolysis of the polypeptide chain after lysine-15 residue in the -DDDDK15- sequence. In 1998 we found an unusual calcium-dependent autolysis of the enteropeptidase heavy chain leading to the drastic loss of its activity towards trypsinogen: after lysine-360 (-NNYEK360-INCN-), -), arginine-384 (-NEWER384-TQGS-), arginine-422 (-GRRER422-VGLL-) and lysine-465 (-QNMEK465-TIFQ-) residues. We used hepta-nona-peptides as the model substrates for autolysys: human angiotensin II--DRVYIHPF and cattle hemoglobin b-chain fragments: LTAEEKA and MLTAEEKAA. Kinetic parameters of enteropeptidase hydrolysis for these substrates were determined. Recent study demonstrates the ability of enteropeptidase to hydrolyze peptide bonds formed by carboxyl groups of Lys or Arg residues if less than four but at least one negative charged amino acid residue is in any of substrate P2-P5 positions. Ca(2+)-dependent autolysis of enteropeptidase heavy chain and of trypsin were compared; the second one serves as the natural defense mechanism against the undesirable premature proenzymes activation in pancreas leading to pancreatitis. The corresponding enteropeptidase inactivation in low Ca2+ environment ought to be the component of the same protective mechanism.

A procedure of isolation of human blood plasma prekallikrein, coagulation factor XII and active fragment beta-XIIa has been developed. This procedure includes the traditional chromatography steps and FPLC. Disc-electrophoresis revealed that the preparations of factor XII and beta-XIIa were homogeneous. Their specific activity was 70.6 U and 2.5 U, respectively. The procedure described is less time consuming and it allows to isolate these factors in the preparative quantities.

Retrotransposones are mobile genetic elements occurring in genomes of bacteria, plants or animals. Retrotransposones were found to contain nucleotide sequences encoding proteins which are homological to retroviral aspartic proteinases. Our research has been focused on Ulysses which is mobile genetic element found in Drosophila virilis. We suggested a primary structure of Ulysses proteinase using comparative analysis of amino acid sequences of retroviral proteinases and proteinases from retrotransposones. The appropriate cDNA fragment has been cloned and expressed in E. coli. The purification of recombinant protein (12 kD) has been carried out by affinity chromatography using pepstatine-agarose. The obtained protein has proteolytic activity at optimum pH 5.5 like the majority of aspartic proteinases.

The site-directed mutagenesis in the S1'-pocket of Thermoactinomyces vulgaris carboxypeptidase T was performed and two variants containing double D253S, T255D and single T255D mutations were obtained. Precursors of the wild-type carboxypeptidase T and its mutant derivatives were expressed in Escherichia coli as inclusion bodies, refolded, activated by subtilisin, purified by gel efiltration on Superdex G-75. The catalytic activity with tripeptide substrates DNPAAR and ZAAL was analysed. The introduction of the aspartic residue in 255 position (like to mammalian carboxypeptidase B), insigniticantly enzymatic activity of the double mutant towards both substrates, as measured by Km and Kcat. An addition of the aspartic residue into S1'-binding pocket did not affect single mutant binding with the basic substrate while the Km value for the hydrophobic substrate increased approximately 40 times as compared with wild-type carboxypeptidase T and attained a level comparable with carboxypeptidase B.