Strepogenin Activity of Synthetic Peptides Related to Oxytocin

Abstract
A number of synthetic peptides representing various sequences occurring in oxytocin were assayed for strepogenin activity with Lactobacillus casei. The activities (units/mg) were: oxytocin 300; the disulfides of: Ileu-Glu(NH2)-Asp(NH2)-CySH-Pro-Leu-Gly(NH2) 250, Ileu-Glu(NH2)-Asp(NH2)-CySH-Pro-Leu-Gly 190, Glu(NH2)-Asp(NH2)-CySH-Pro-Leu-Gly(NH2) 35-130, isoGlu(NH2)-Asp(NH2)-CySH-Pro-Leu-Gly(NH2) 10, Asp(NH2)-CySH-Pro-Leu-Gly(NH2)20, Ileu-Glu(NH2)-Asp(NH2)-CySH-Pro(NH2) 30, Ileu-Glu(NH2)-Asp(NH2)-CySH(NH2) 15, CySH-Pro-Leu-Gly(NH2)<3; neu-Glu(NH2)-Asp(NH2)<3, and Glu(NH2)-Asp(NH2)<2. The bearing of these findings on the question of nutritional requirements for specific peptides was discussed.