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  • 1
    Electronic Resource
    Electronic Resource
    The Proteolytic Activity and Cleavage Specificity of Fibronectin-Gelatinase and Fibronectin-Lamininase (1999)
    Springer
    The protein journal 18 (1999), S. 403-411 
    Details
    ISSN: 1573-4943
    Keywords: Fibronectin ; FN-gelatinase ; FN-lamininase ; retroviral aspartic proteinases ; α2-macroglobulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Human plasma fibronectin contains two latent aspartic proteinases, FN-gelatinase and FN-lamininase. Both enzymes can be generated and activated in the presence of Ca2+ from the purified cathepsin D-produced 190-kDa fibronectin fragment. We investigated the proteolytic activity and cleavage specificity of both enzymes in a range of pH from 3.5 to 9.0 using the B chain of oxidized bovine insulin and chromogenic peptides as substrates. The inhibition of the enzymes by several natural inhibitors from human plasma was also tested. The specificities of FN-gelatinase and FN-lamininase are similar to other major acidic proteinases, including pepsin, renin, cathepsin D, and HIV-proteinases. Both enzymes mainly hydrolyze three peptide bonds in the oxidized insulin B chain, namely Glu–Ala (residues 13–14), Tyr–Leu (residues 16–17), and Phe–Phe (residues 24–25). For the peptide substrates H-Pro-Thr-Glu-Phe-p-nitro-Phe-Arg-Leu-OH and H-Phe-Gly-His-p-nitro-Phe-Phe-Val-Leu-OMe that were cleaved the respective values of k cat/K M were 105.1 and 11.8 mM−1 sec−1 for cleavage by FN-gelatinase, and 123.2 and 15.5 mM−1 sec−1 for cleavage by FN-lamininase. The maximal activities of both enzymes were observed in a range between pH 5.6 and 6.3 and they became inactivated at a pH value above 8.4. Both FN-gelatinase and FN-lamininase were efficiently inhibited by α2-macroglobulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020684508212
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of Tryptase TL2 from Human T4+ Lymphocytes and Inhibition of HIV-1 Replication in H9 Cells by Recombinant Aprotinin and Bikunin Homologues (1997)
    Springer
    The protein journal 16 (1997), S. 651-660 
    Details
    ISSN: 1573-4943
    Keywords: Kunitz-type inhibitor ; aprotinin ; bikunin ; tryptase TL2 ; HIV infection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The serine esterase TL2 from human T4+ lymphocytes is a binding component to HIV-1 glycoprotein gp120 and seems to play a role in the HIV-1 infection mechanism. Recombinant variants of the Kunitz-type serine proteinase inhibitor aprotinin were investigated for their ability to inhibit tryptase TL2 and the binding of gp120 to this enzyme. Furthermore, the viral replication of HIV-1 was investigated in H9 cell cultures under the influence of recombinant aprotinin and bikunin variants. In contrast to native aprotinin, the recombinant variant [Arg15, Phe17, Glu52]aprotinin with a reactive-site sequence homologous to the V3 loop of HIV-1 gp120 showed a specific inhibition of tryptase TL2 (〉80%). However, the [Leu15, Phe17, Glu52]aprotinin variant with hydrophobic subsites was the most potent inhibitor of the binding of gp120 to tryptase TL2 (68%). Our results show that the enzyme activity of purified tryptase TL2 is inhibited not only by variants with basic amino acids, but also those with hydrophobic residues in the reactive-site region. Therefore, tryptase TL2 is not a typical trypsin-like or chymotrypsin-like protease. Investigations on inhibition of HIV-1 replication in H9 cell cultures showed that tryptase TL2 is involved in the mechanism of virus internalization into human lymphocytes. The [Leu15, Phe17, Glu52]aprotinin showed a significant retardation of syncytium formation over a period of 5 days in a 1 μM concentration. Similar investigations were performed with recombinant variants of bikunin, the light chain of human inter-α-trypsin inhibitor. Only the single-headed variant [Arg94]82bikunin inhibited slightly the syncytium formation over a period of 2 days in a 2.2 μM concentration. Wild-type bikunin and all full-length variants showed no effect, possibly due to steric hindrance by the second domain of the double-headed inhibitor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026379109403
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    Paper (German National Licenses)
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