Ichizo Shinoda

LACTOFERRIN AS A SUPPRESSOR OF CELL MIGRATION OF GASTROINTESTINAL CELL LINES

The effects of lactoferrin (Lf), an iron‐binding glycoprotein, on cell migration were investigated. Lf inhibited the cell migration of three gastrointestinal cell lines (Caco‐2 cells, AGS cells, and IEC‐18 cells) in vitro. Both iron‐saturated (holo) and iron‐depleted (apo) Lf showed this inhibitory effect. Chelation of iron in the culture medium by desferrioxamine did not affect the activity of either form of Lf. A pepsin hydrolysate of Lf exhibited effectiveness similar to that of intact Lf. These results demonstrate a novel activity of Lf and suggest a potential role for this molecule in gastrointestinal wound healing, which is independent of its iron‐binding capacity. J. Cell. Physiol. 170:101–105, 1997.

Inhibitory Effect of Bovine Lactoferrin on Catechol-O-Methyltransferase.

Lactoferrin (LF) is a well-known multifunctional protein. In this study, we report the inhibitory potency of bovine LF (bLF) on catechol-O-methyltransferase (COMT), which catalyzes methylation of catechol substrates. We found that bLF binds to and inhibits COMT using its N-terminal region. An N-terminal peptide fragment obtained from bLF by trypsin digestion showed a higher inhibitory activity than intact bLF. A synthetic fragment of the bLF N-terminal residues 6–50, with two pairs of disulfide bonds, also showed higher inhibitory activity than intact bLF. Enzyme kinetic studies proved that bLF did not compete with S-adenosylmethionine (the methyl donor substrate) as well as methyl acceptor substrates such as dihydroxybenzoic acid, (−)-epicatechin, norepinephrine, or l-3,4-dihydroxyphenylalanine. The inhibitory potency of bLF decreased against a COMT preparation pretreated with dithiothreitol, suggesting that the oxidation status of COMT is relevant to interaction with bLF. We further confirmed that COMT activity in the cell extracts form Caco-2 and HepG2 cells was inhibited by bLF and by the synthesized fragment. Enzyme kinetic study indicated that bLF functions as a non-competitive inhibitor by binding to an allosteric surface of COMT.