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Metal‐Combining Properties of Human Lactoferrin

1972; Wiley; Volume: 31; Issue: 2 Linguagem: Inglês

10.1111/j.1432-1033.1972.tb02526.x

1432-1033

B. Teuwissen, Pierre Masson, Pierre A. Osinski, J.F. Heremans,

Pediatric Hepatobiliary Diseases and Treatments

By means of a Spectrophotometric titration method it was found that six of the tyrosyl residues of the metal‐binding proteins lactoferrin and transferrin were titratable by alkali in the metal‐free proteins but not in their iron protein complexes, suggesting the involvement of three tyrosyl groups in each of the two binding sites present in these proteins. Seemingly discordant estimates of the number of binding tyrosyls were obtained using the difference spectra of the lactoferrin · Tb 3+ vs lactoferrin, lactoferrin · Fe 3+ vs lactoferrin, transferrin · Tb 3+ vs transferrin or transferrin · Fe 3+ vs transferrin. However, such discrepancies as were found could be explained in the light of the ligand‐field theory and need not invalidate the conclusions based on alkali‐titration data.