Isolation and Partial Characterization of Adipotropin, an Apparent new Lipolytic Peptide from Bovine Anterior Pituitary Lobes

A Dentide. aDDarentlv new. has been isolated from the anterior lobes of bovine pituitary glands by the following steps:(1) lyophilization of frozen tissue; (2) homogenization; (3) extraction with an aqueous buffer; (4) gel filtration; (5) anion and then (6) cation exchange chromatography; (7) HPLC. One antioxidant and two proteolytic inhibitors were present during buffer extraction to avoid artifactual reactions. Amino acid analyses consistently revealed the same amino acids and no others on different specimens, one year apart. The composition was estimated as: 4 Asp, 2 Thr, 5 Ser, 8 Glu(x), 5 Pro, 10 Gly, 4 Ala, 2 Val, 2 Met, 1 Ile, 2 Leu, 1 Tyr, 1 Phe, 2 His, 3 Lys, 2 Arg (5600 daltons). Cysteine and tryptophan were absent. An approximate molecular weight by gel filtration was 7200 daltons. The isoelectric point was 6.1. The peptide showed a dose-response activity in the range of 0.001-1.0 μg in a rabbit adipose system, in vitro. The peptide is tentatively designated as adipotropin, because it has no unequivocal chemical relationship to other relevant lipolytic peptides, and because it has the highest molar potency, in vitro, of these peptides, including pACTH.