Purification and characterization of bovine lactoferrin from secretions of the involuting mammary gland: identification of multiple molecular weight forms.

1. Lactoferrin was isolated from bovine mammary secretions collected during the nonlactating period. 2. A method utilizing heparin-agarose affinity chromatography was more efficient for purifying lactoferrin than a method including gel filtration, ion exchange chromatography and a second gel filtration. 3. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the purified lactoferrin was composed of two protein bands of apparent mol. wt. of 83,000 and 87,000. 4. Digestion with endoglycosidase H resolved the lactoferrin into two lower mol. wt. bands of 78,000 and 81,000. 5. The biochemical differences between the forms of lactoferrin are not exclusively due to differences in endoglycosidase H-sensitive oligosaccharide composition.