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Biomedical subjects

S Bajusz

Publications and source records attributed to S Bajusz.

At least 55 records · Page 3Linked to original sources
PubMed1984

Met5-enkephalin-Arg6-Phe7 inhibition of noradrenaline and acetylcholine release from peripheral organs.

The effect of the opioid heptapeptide Met5-enkephalin-Arg6-Phe7 was measured on the contractions of the longitudinal muscle of the guinea-pig ileum and mouse vas deferens; on release of endogenous and newly synthesized acetylcholine from the longitudinal muscle strip preparation of the guinea-pig ileum and of 3H-noradrenaline from mouse vas deferens. Met5-enkephelin-Arg6-Phe7 depressed the contractions of the longitudinal muscle strip of guinea-pig ileum elicited by low frequency stimulation (IC50 366.5 +/- 71.5 nM). The Ke value of naltrexone against the heptapeptide was found to be 0.50 +/- 0.08 nM. Bestatin prolonged and strongly potentiated the action of the opioid peptide in this tissue while captopril proved to be only slightly effective. Met5-enkephalin-Arg6-Phe7 also inhibited neuroeffector transmission in the mouse vas deferens with an IC50 value of 9.44 +/- 2.24 nM. The Ke value of naltrexone was 6.33 +/- 1.22 nM against the heptapeptide. Met5-enkephalin-Arg6-Phe7 (10(-5) M) failed to affect the low frequency stimulated release of endogenous acetylcholine from the guinea-pig ileum preparation. Addition of either bestatin or captopril with the heptapeptide resulted in a reduction of acetylcholine output. The opioid peptide by itself decreased the release of newly synthesized acetylcholine outflow from this organ. Met5-enkephalin-Arg6-Phe7 also reduced the 3H-noradrenaline outflow from mouse vas deferens and this effect was antagonized by naltrexone. From our data we conclude that Met5-enkephalin-Arg6-Phe7 affects the neural transmission of peripheral autonomically innervated organs by depressing the release of neurotransmitter. In vitro it has enkephalin-like character with a preference for the so called delta receptor interaction.

Acetylcholine↗
PubMed1982

Design and synthesis of peptide inhibitors of blood coagulations.

Inhibition of blood coagulation by peptide aldehydes has been studied. Amino acid sequences were assembled from the P1-P2 portion of the cleavage sites(s) of clotting factors and residues selected experimentally. The thrombin-fibrinogen reaction could effectively be inhibited by D-Phe-Pro-Arg-H (GYKI-14,166) and Boc-D-Phe-Pro-Arg-H (GYKI-14,451). Plasmin digestion of fibrin could be retarded by Boc-Gln-Phe-Lys-H (GYKI-14,605) derived from a susceptible fragment, i.e. Asn-Phe-Lys decreases to Ser. However, such peptides could not retard the zymogen activations proceeding in Ca++ complexes (which seemed to be uneffected by heparin-antithrombin III, too). Inhibition of enzymes by peptide aldehydes showed marked substrate dependence.

Amino Acid Sequence↗
PubMed1981

Enkephalin-like character and analgesia.

The opioid activities of enkephalin analogues bearing D- or L-aminopentane-sulfonic/phosphonic acid at position 5 were studied in vitro, in electrically stimulated longitudinal muscle strip of guinea-pig ileum and mouse vas deferens preparations and in vivo in the rat tail-flick test. Using their in vitro effects Met-enkephalin-like, beta-endorphin-like, (nor)morphine-like and derivatives of intermediate character could be differentiated. Correlating the in vitro activities with the analgesic activity in vivo it is concluded that the enkephalin-like character in a pentapetide may hinder the expression of analgesic activity, when the compounds are given into the cerebroventricular system.

Analgesics↗
PubMed1981

Study of the specificity of thrombin with tripeptidyl-p-nitroanilide substrates.

The kinetic behaviour of human thrombin has been studied with 26 tripeptidyl-p-nitroanilide substrates protected at the N terminus and with 9 unprotected ones. By the regression analysis of experimentally determined 1/Km, kcat and kcat/Km values the individual contribution of each side chain of the various substrates to the kinetic parameters was calculated. The contributions to the kinetic parameters of the best substrates provide information about the structure of the binding site. The interaction of subsites S1 and P1, which determines primary specificity, proved to be marginal on the basis of contribution values, though it depends upon this contact whether the substrate is hydrolyzed at all. At subsite S2 proline appeared to be favourable. Subsite S3 plays an important role in efficiency. The best parameters were obtained here with the D configurations of bulky amino acid residues. The aromatic protecting groups applied did not improve the properties of substrates. BZDPhe-Pro-Arg-Nan was predicted by calculation to be better than the protected substrates assayed. The compound was synthesized and tested. Its experimentally determined 1/Km, 55.1 mM-1, was in good agreement with 50.9 mM-1 found by calculation.

Anilides↗
PubMed1981

Investigation of the substrate-binding site of trypsin by the aid of tripeptidyl-p-nitroanilide substrates.

The kinetic parameters of the tryptic hydrolysis of tripeptidyl-p-nitroanilide substrates were determined and the data were studied by regression analysis. The sequence of substrates optimal from the viewpoint of kinetic constants 1/Km, kcat and kcat/Km was established and the influence of amino acid side chains on the binding and reactivity of substrates was calculated. At subsite P3 [notation of Schechter and Berger (1967) Biochem. Biophys, Res. Commun. 27, 157] polar side chains (Asn, D-Arg) are favourable as regards 1/Km, whereas hydrophobic side chains are preferred definitely from the viewpoint of catalytic efficiency, just as at subsite P2. In the side chain contributions, calculated for the kinetic parameters, the P3-S3 interaction predominates, in spite of the fact that the properties of the residue at subsite P1 decide whether hydrolysis occurs at all. The ZAsn-Ile-Arg-Nan sequence was predicted as a better substrate than those tested experimentally. The compound was synthesized, and the calculated value of its 1/Km (116.4 mM-1) was in a good agreement with the measured value (100.2 mM-1). Comparing the data obtained with trypsin with those observed with thrombin, elastase and subtilisin, we can establish that the homology of these enzymes can be characterized at each binding subsite by the aid of tripeptidyl-p-nitroanilide substrates. The quantities derived allow one to envisage a novel type of comparison of the proteases.

Anilides↗
PubMed1980

Alternative synthesis of corticotropin-like intermediate lobe peptide (human CLIP). A peptide corresponding to the sequence of human ACTH-(18--39).

A novel synthesis of human CLIP, a peptide corresponding to the sequence of human ACTH-(18-39) is described. The dodecapeptide chain was assembled by a combination of fragment condensation and stepwise synthesis while using N alpha-benzyloxycarbonyl and side chain tert.-butyl-derived protective groups combination. The final deprotection was performed by acidolysis in trifluoroacetic acid. The end product was purified by ion exchange chromatography on carboxymethyl cellulose.

Adrenocorticotropic Hormone↗