Insulin-like growth factor I (IGF-I) from cow colostrum: purification and characterization.

Insulin-like growth factor I (IGF-I) has been purified from defatted cow colostrum. The purification procedure involved cation exchange chromatography on CM Affigel blue, acid gel-filtration and two HPLCs. This purification process constitutes a significant improvement, in terms of yield and rapidity, over the previously reported procedures. Purified IGF-I was found to be 95% pure by N-terminal amino acid sequence analysis. After isolation of peptides from a digest of IGF-I obtained using staphylococcus aureus protease, the complete sequence was established and found to be identical to that of bovine or human plasma IGF-I.