The isolation and structure of alpha-melanocyte-stimulating hormone from horse pituitaries

It has been possible to isolate alpha(c)-MSH in highly purified form from the posterior lobes of horse pituitaries by a new awl simplified method which makes use of counter-current distribution in a solvent system consisting of 0.1% acetic acid, n-butanol and pyridine, mixed in the volume ratio of 11:5:3. In this solvent system. the hormone distributes with a partition coefficient of 1.30. By the frog-skin assail method, alpha(e)-MSH possesses an activity of 1.0 X 10(10) units per gram. In addition, this molecule has been characterized by means of terminal residue and amino acid analyses as well as on the basis of the results of enzymic digestion. In every respect, alpha(c)-MSH was shown to be identical with alpha-MSH from beef pituitaries. A partial amino-acid sequence has been proposed for alpha(e)-MSH; it appears very probable that the equine alpha-MSH has a structure identical to that previously proposed for alpha-MSH isolated from beef and pig pituitaries.