THE SEQUENCE OF AMINO ACIDS IN OXYTOCIN, WITH A PROPOSAL FOR THE STRUCTURE OF OXYTOCIN

Abstract

Previous communicationsfrom this laboratory have shown that oxytocin hydrolysates contain leucine, isoleucine, tyrosine, proline, glutamic acid, aspartic acid, glycine, and cystine in equimolar ratios to each other and ammonia in a molar ratio to any one amino acid of 3: 1 (1, 2).The sequence of these amino acids in oxytocin has now been investigated through partial hydrolysis studies of oxytocin, of desulfurized oxytocin, and of the large fragment resulting from treatment of performic acid-oxidized oxytocin (3) with bromine water (4, 5).The resulting peptides were separated into acidic and neutral components by use of ion exchange resins and were then further separated by paper chromatography.The composition of the various peptides was determined by elution, hydrolysis, and analysis for amino acids by paper chromatography.On the basis of these data along with other information such as that derived from utilization of the Edman degradation (6) and from the cleavage with bromine water (5), together with certain assumptions which will be mentioned, a tentative structure for oxytocin is proposed.EXPERIMENTAL