New functions of lactoferrin and beta-casein in mammalian milk as cysteine protease inhibitors

Biochem Biophys Res Commun. 2003 Jun 20;306(1):98-103. doi: 10.1016/s0006-291x(03)00917-3.


We found new inhibitory function of lactoferrin and beta-casein in milk against cysteine proteases using reverse zymography. The inhibition of cathepsin L by lactoferrin was strongest and the inhibition kinetics were of a non-competitive type. Heat denatured lactoferrin lost the inhibitory activity completely, therefore the tertiary structure is essential to show the inhibition. Native lactoferrin was not degraded by papain during the assay condition. The intramolecular peptide, Y(679)-K(695), of lactoferrin is an active domain and the synthesized peptide inhibited cysteine proteases. The Y(679)-K(695) peptide showed 90% homology with the sequences of a common active site of cystatin family. beta-Casein and the active domain, synthesized L(133)-Q(151), peptide inhibited cysteine proteases. Lactoferrin and beta-casein in milk might play a role in antiseptic and antiinfectious functions due to cysteine protease inhibition of bacteria and viruses.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Caseins / chemistry
  • Caseins / genetics
  • Caseins / metabolism*
  • Cattle
  • Cysteine Endopeptidases / metabolism
  • Cysteine Proteinase Inhibitors / chemistry
  • Cysteine Proteinase Inhibitors / genetics
  • Cysteine Proteinase Inhibitors / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Female
  • Humans
  • In Vitro Techniques
  • Kinetics
  • Lactoferrin / chemistry
  • Lactoferrin / genetics
  • Lactoferrin / metabolism*
  • Milk / metabolism*
  • Milk, Human / metabolism
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Rats
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid


  • Caseins
  • Cysteine Proteinase Inhibitors
  • Recombinant Proteins
  • Lactoferrin
  • Cysteine Endopeptidases