STUDIES ON THE CARBOXYL-TERMINAL PEPTIDES OF HUMAN SEMINAL PLASMA INHIBIN (HSPI) - CHEMICAL SYNTHESIS AND IN-VIVO BIOLOGICAL-ACTIVITY OF THE DISULFIDE LOOP PEPTIDE 67-94 OF HSPI

Observation of contradictory results with the in vitro assays for inhi bin-like activity of the carboxyl terminal 28 amino acid peptide 67-94 with a disulfide loop, of human seminal plasma inhibin (HSPI), prompt ed us to synthesize both the linear and the cyclic peptides and test t heir ability to suppress the circulating levels of follicle stimulatin g hormone (FSH) in vivo in adult male rats. The linear peptide [Cys(Ac m)73,87] 67-94 of HSPI was synthesized by solid-phase peptide synthesi s using fluorenylmethyloxycarbonyl (Fmoc) chemistry and a continuous-f low technology. The peptide was cyclized by direct iodine oxidation of the S-diacetamidomethyl peptide in dilute solution. In the in vivo as say the linear peptide did not affect the levels of FSH, whereas the c yclic peptide suppressed the revels of FSH significantly. Thus, the ca rboxyl terminal region of HSPI does have inhibin-like activity and per haps has the active core of the protein. (C) Munksgaard 1993.