The Isolation and Characterization of Methionine Sulfoxide Analogues of α- and β-Melanocyte-Stimulating Hormones from Bovine and Equine Pituitary Glands

Abstract

The polypeptide concentrates from the posterior-intermediate lobes of bovine and equine pituitary glands have been studied extensively by countercurrent distribution. Various active peptides, namely, β-MSH, vasopressin, α-MSH, and adrenocorticotropin, have been resolved by countercurrent distribution in two different system, 0.1%, acetic acid: n-butanol: pyridine (11:5:3), and 0.5% aqueous triehloroacetic acid: 2-butanol. In addition to the above-mentioned known peptide hormones, the isomers corresponding to α- and β-MSH have been isolated. These isomers showed poor malanocyte-stimulating activity compared with known α- and β-MSH. They were found to be methionine sulfoxide analogues of the latter. The presence of methionine sulfoxide instead of methionine in these analogues was demonstrated by amino acid analyses of alkaline hydrolysates and enzymatic digests, as well as from oxidation-reduction behavior correlated with biological activity.