Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The subcellular location of the major malarial glycoprotein in erythrocytes infected with schizonts of Plasmodium falciparum has been studied by two methods. In the first, glycoproteins were labelled with [3H]glucosamine or [3H]isoleucine during in vitro culture. Trypsin treatment of intact infected erythrocytes caused no major qualitative or quantitative changes in [3H]glucosamine labelled glycoproteins or [3H]isoleucine labelled proteins separated by sodium dodecylsulfate polyacrylamide gel electrophoresis. However, in the presence of Triton X-100 the labelled glycoproteins and proteins were completely cleaved by trypsin. In the second method, two monoclonal antibodies which specifically immunoprecipitate the major 195 kDa glycoprotein failed to react on indirect immunofluorescence with intact non-fixed schizont-infected erythrocytes, but reacted strongly with saponin released schizonts indicating specificity for the surface of mature intracellular parasites. Immunoelectronmicroscopy using ferritin-conjugated secondary antibody confirmed the location of the epitope(s) recognized by these monoclonals on the surface of intracellular parasites. Ferritin particles were not associated with knob-bearing erythrocyte membranes. The results indicate that only a small proportion or none of the 195 kDa glycoprotein is on the surface of the infected erythrocyte and that the largest proportion is expressed on the surface of mature intraerythrocytic parasites.
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PMID:Localization of the major Plasmodium falciparum glycoprotein on the surface of mature intraerythrocytic trophozoites and schizonts. 637 50

Virgin and modified [single peptide bond between arginine (63) and isoleucine (64) is cleaved] soybean anti-trypsin was separated by chromatofocusing using a narrow pH range. The separation on anion-exchange and reversed-phase chromatography was less satisfactory. Anti-proteases isolated by affinity chromatography from Boophilus decoloratus were monitored for the formation of any modified protein, with chromatofocusing.
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PMID:Determination of anti-protease homogeneity. 649 Jul 68

This study was initiated to characterize PHI (peptide histidine isoleucine amide)-27-like peptides (PLPs) in rat and porcine brain in comparison with other members of the vasoactive intestinal polypeptide (VIP) family and to investigate their distribution by radioimmunoassay. The peptidic nature of the rat brain PLP was indicated by its trypsin sensitivity. On Sephadex chromatography rat brain PLP has the same molecular weight as synthetic (porcine intestinal) PHI-27. High pressure liquid chromatographic separations revealed that PLP in rat and porcine brain extracts elutes as a single peak distinct from VIP or secretin. Porcine brain PLP elutes in the same position as synthetic PHI-27, whereas rat brain PLP immunoreactivity consistently separates from synthetic PHI-27. This suggests that porcine brain PLP is identical to synthetic PHI-27, in agreement with the reported sequence of Tatemoto et al. (Tatemoto, K., M. Carlquist, T. McDonald, and V. Mutt (1983) FEBS Lett. 153: 248-252), whereas PLP may have a different amino acid sequence (or may be post-translationally modified). Using specific PHI and VIP radioimmunoassays, the distribution of PLP was found to parallel that of VIP in rat and porcine brain, being highest in cerebral cortex, amygdala, and hippocampus. PLP, like VIP, is abundant in rat retina and can be included in the growing list of retinal peptides. This highly correlated distribution of VIP and PLP may be explained by the recent discovery that they are derived from the same precursor (Itoh, N., K. Obata, N. Yanaihara, and H. Okamoto (1983) Nature 304: 547-549).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The distribution and chromatographic characterization of PHI (peptide histidine isoleucine amide)-27-like peptides in rat and porcine brain. 654 67

Hirudin from whole leeches behaves like hirudin from leech heads and "pseudohirudin" from leech bodies during isolation and purification by means of acetone and ethanol fractionation, affinity chromatography on trypsin-Sepharose, and isoelectric focusing. However, the antithrombin activity of the hirudin fractions obtained after isoelectric focusing was approximately three times lower than that of the corresponding hirudin fractions from the heads. The "pseudohirudin" fractions had practically no antithrombin activity. In hirudin from whole leeches isoleucine and valine were identified as the N-terminal amino acid. Isoleucine was identified as the dominant amino acid in hirudin from leech heads. The dominant N-terminal amino acid in "pseudohirudin" from leech bodies was valine. The data on antithrombin activity and N-terminal amino acids indicate that hirudin from whole leeches contains admixtures of inactive "pseudohirudin". In contrast to hirudin from leech heads, "pseudohirudin" represents associates of di- and three-isomers. The molecular weight of the "pseudohirudin" molecule is 2000 lower than the molecular weight of hirudin, which corresponds to a difference of 20 amino acid residues, calculated from the total number of amino acid residues in the preparations.
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PMID:Hirudin from leech heads and whole leeches and "pseudo-hirudin" from leech bodies. 661 79

The complete amino acid sequence of a lectin from sainfoin ( Onobrychis viciifolia Scop . var. Eski ) has been determined by sequential Edman analyses of the intact protein and peptides derived from digests with trypsin and thermolysin. Peptides were purified by pH fractionation, by gel filtration, and by cation-exchange and reverse-phase high-performance liquid chromatography. Seven segments of continuous sequence, accounting for the entire protein, were aligned through sequence comparison with several homologous leguminous lectins to give the final structure. Sainfoin lectin monomer, a glycoprotein which contains a single polypeptide chain of 236 amino acid residues with a molecular weight of 26 509, has amino- and carboxyl-terminal residues of alanine and threonine, respectively. A single residue of cysteine, located at position 33, is the only sulfur-containing amino acid present. Asparagine-118 is the single oligosaccharide attachment site. At least two apparent allelomorphic forms of the protein, having valine or isoleucine at position 49 in equal amounts, were detected. The amino acid sequence of sainfoin lectin exhibits circular permutation relative to that of the homologous protein concanavalin A.
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PMID:Lectin from sainfoin (Onobrychis viciifolia scop.). Complete amino acid sequence. 672 25

Protein S, a development-specific protein of Myxococcus xanthus, was purified from the cells of a late stage of development and crystallized. Its circular dichroism spectra indicated that protein S had a high content of beta-structure in both the presence and absence of calcium ion, which is required for self-assembly of protein S on the myxospore surface. Its amino and carboxyl terminal sequences were determined to be alanine-aspartic acid-isoleucine-glycine-valine-alanine-methionine-asparagine-asparagine-aspartic acid-threonine-serine-serine and isoleucine-arginine (isoleucine, serine), respectively. When protein S (molecular weight, 23,000) was digested with trypsin, a trypsin-resistant core of 10,000 molecular weight was obtained. The core peptide was purified, and its amino acid composition was compared with that of protein S. The core peptide was capable of self-assembly on the spore surface in the presence of calcium ion and competed with protein S for binding on the spore surface. The ratio of affinity to the spore surface for protein S to that for the core peptide was 1.55.
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PMID:Development-specific protein S of Myxococcus xanthus: purification and characterization. 679 83

T-kinin, a previously undescribed peptide containing bradykinin, has been isolated following treatment of rat plasma with trypsin (1 mg/ml). The liberated T-kinin, which contracts the rat uterus, was isolated by procedures including OM-cellulose, Biogel P-4 and reverse-phase high-performance liquid chromatography. The final material had a single N-terminal isoleucine and was shown by amino acid analysis and sequence determination to have the structure of the undecapeptide Ile-Ser-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (isoleucyl-seryl-bradykinin). The relationships of the protein from which T-kinin is cleaved (T-kininogen) to other known kininogens is discussed.
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PMID:Isolation and structure of T-kinin. 684 71

The subsite specificities of bovine factor IXa, factor Xa, factor XIa, factor XIIa, thrombin, plasma kallikrein, and trypsin were mapped with amino acid, dipeptide, and longer peptide thioester substrates. Each substrate contained a P1 Arg residue. The P1' residues included thiol residues which are analogues of valine, leucine, and isoleucine, respectively, and the P2 residue included 12 representative amino acid residues. Longer substrates with the sequence at the antithrombin III reactive site and at the zymogen activation site of various coagulation factors were also studied. The enzymatic hydrolysis of the thioesters was measured in the presence of 4,4'-dithiodipyridine which provides a very sensitive assay for the free thiol. The thioesters were excellent substrates for the coagulation factors studied, and the kcat/Km values for the best thioester substrates were higher than those previously reported for most of these enzymes. Thrombin and plasma kallikrein were the most active of the coagulation factors toward the thioester substrates. The best substrate for thrombin was Z-Gly-Arg-SCH2C6H5, although substrates containing proline in the P2 position were also quite effective. Some of the better substrates for plasma kallikrein had a P2 Phe or Trp residue. Factor IXa was the least reactive of the coagulation factors and hydrolyzed only four of the dipeptide thioesters. Substrates with bulky hydrophobic groups such as Phe or Trp in the P2 position were the most reactive with factor IXa. Factor Xa hydrolyzed all the thioester substrates tested, the most reactive being Z-Gly-Arg-SCH2C6H5. This is consistent with the fact that glycine and arginine are present in the P2 and P1 positions, respectively, of the factor Xa sensitive bonds in prothrombin which is the physiological substrate for factor Xa. Bovine factor XIa showed the least amount of specificity of the various coagulation factors and was quite reactive toward all of the thioester substrates. The most sensitive substrate for this enzyme was also Z-Gly-Arg-SCH2C6H5. Factor XIIa preferred the dipeptide with a P2 Phe, although the simpler thioester Z-Arg-SCH2CH(CH3)2 was more reactive. Trypsin hydrolyzed all of the thioester substrates at a high rate and showed little substrate specificity. With all enzymes studied, extension of the thioester substrate beyond P2 or the P1' thiol leaving group did not lead to an improvement in hydrolysis. Due to their high kcat/Km values and the ease of detecting the thiol leaving group, thioester substrates should be extremely useful for future studies of coagulation proteases.
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PMID:Mapping the active sites of bovine thrombin, factor IXa, factor Xa, factor XIa, factor XIIa, plasma kallikrein, and trypsin with amino acid and peptide thioesters: development of new sensitive substrates. 697 85

Crude extracts of porcine cerebral cortical tissue convert cholecystokinin (CCK) to its COOH-terminal fragments, the dodecapeptide (CCK-12) and the octapeptide (CCK-8). The Sephadex G-75 void volume eluate of the crude extract cleaves the arginine-isoleucine bond and effects conversion only to CCK-12; the Sephadex G-50 void volume eluate of the same extract cleaves the arginine-aspartate bond as well, so that both CCK-12 and CCK-8 are end products. Thus, there are at least two enzymes; the one involved in the conversion to CCK-12 is of larger molecular radius than the other. The Km for the cleavage of CCK at the arginine-isoleucine bond by the Sephadex G-75 void volume eluate enzyme is 1.1 X 10(-6) M; the Km for trypsin cleavage of the same bond is 4.7 x 10(-6) M. The lower Vmax for the brain enzyme (1.5 x 10(-11) mol/min per g of extract) compared with trypsin (66 x 10(-11) mol/min per g of trypsin) simply reflects the lesser degree of purify of the brain extract than of the highly purified trypsin.
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PMID:Cholecystokinin-converting enzymes in brain. 698 59

The mode of action of colicin S8 has been studied and compared with that of other colicins. Two minutes after the addition of colicin S8 to bacteria a considerable proportion of the colicin is inaccessible to trypsin. Treatment of bacteria with colicin S8 renders them more sensitive to lysis by sodium dodecyl sulphate and also inhibits motility. Like colicins K and E1, colicin S8 provokes lysis of bacteria superinfected with bacteriophage T4. Colicin S8, unlike colicin E2, prevents replication of bacteriophage T4. The incorporation of isoleucine or uracil into bacteria is inhibited by colicin S8 but, unlike colicins K and E1, the effect is multiplicity-dependent. A rapid method of titration of colicin S8 is described. The results are discussed with emphasis on the possible rearrangements at the bacterial surface and the possibility that there is more than one type of specific receptor for colicin S8.
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PMID:Mode of action of colicin S8. 705 Feb 99


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