Proteolytic activity of bovine lactoferrin.
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.
Massucci
Maria Teresa
MT
Dipartimento di Biologia di Base ed Applicata, Universita' di L'Aquila, Coppito, 67010, L'Aquila, Italy.
Giansanti
Francesco
F
Di Nino
Giovanna
G
Turacchio
Manola
M
Giardi
Maria Federica
MF
Botti
Dario
D
Ippoliti
Rodolfo
R
De Giulio
Beatrice
B
De Giulio
Barbara
B
Siciliano
Rosa Anna
RA
Siciliano
Rosa
R
Donnarumma
Giovanna
G
Valenti
Piera
P
Bocedi
Alessio
A
Polticelli
Fabio
F
Ascenzi
Paolo
P
Antonini
Giovanni
G
D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D006801:Humans; D006867:Hydrolases / Q000378:metabolism*; D007781:Lactoferrin / Q000737:chemistry / Q000378:metabolism*; D008970:Molecular Weight; D012694:Serine / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D012694:Serine; D006867:Hydrolases; D007781:Lactoferrin