Proteolytic activity of bovine lactoferrin |
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Authors: | Maria Teresa Massucci Francesco Giansanti Giovanna Di Nino Manola Turacchio Maria Federica Giardi Dario Botti Rodolfo Ippoliti Barbara De Giulio Rosa Siciliano Giovanna Donnarumma Piera Valenti Alessio Bocedi Fabio Polticelli Paolo Ascenzi Giovanni Antonini |
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Affiliation: | Dipartimento di Biologia di Base ed Applicata, Universita' di L'Aquila, Coppito, 67010, L'Aquila, Italy. |
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Abstract: | Bovine lactoferrin catalyzes the hydrolysis of synthetic substrates (i.e., Z-aminoacyl-7-amido-4-methylcoumarin). Values of Km and kcat for the bovine lactoferrin catalyzed hydrolysis of Z-Phe-Arg-7-amido-4-methylcoumarin are 50 microM and 0.03 s(-1), respectively, the optimum pH value is 7.5 at 25 degrees C. The bovine lactoferrin substrate specificity is similar to that of trypsin, while the hydrolysis rate is several orders of magnitude lower than that of trypsin. The bovine lactoferrin catalytic activity is irreversibly inhibited by the serine-protease inhibitors PMSF and Pefabloc. Moreover, both iron-saturation of the protein and LPS addition strongly inhibit the bovine lactoferrin activity. Interestingly, bovine lactoferrin undergoes partial auto-proteolytic cleavage at positions Arg415-Lys416 and Lys440-Lys441. pKa shift calculations indicate that several Ser residues of bovine lactoferrin display the high nucleophilicity required to potentially catalyze substrate cleavage. However, a definitive identification of the active site awaits further studies. |
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Keywords: | autoproteolysis iron lactoferrin LPS |
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