Comparative studies on the chemical and immunochemical properties of human milk, human pancreatic juice and bovine milk lactoferrin.

Lactoferrin from human milk, pancreatic juice and bovine milk were purified by heparin-Sepharose affinity chromatography procedure. Urea-sodium dodecylsulfate-polyacrylamide gel electrophoresis of these lactoferrin preparations indicated similar molecular weights (80,000). Metal analyses showed that lactoferrin of bovine milk contained the highest amount of iron while lactoferrin of human milk and human pancreatic juice were similar in content of iron, approximately four-fold lower than bovine milk. All these lactoferrin preparations were also found to contain minor amounts of copper and manganese. Double diffusion analyses indicated that lactoferrin of human milk was immunochemically identical to lactoferrin of human pancreatic juice. On the other hand, immunochemically, bovine milk lactoferrin was not identical to human milk lactoferrin. Sequence analyses of human milk and pancreatic juice lactoferrin indicated that they shared the same N-terminal sequence for the 16 residues analyzed. Although human milk and bovine milk lactoferrin had sequence homologies, bovine milk lactoferrin had a closer homology to ovotransferrin than to human milk lactoferrin.