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Synthesis,biological activity and isomerism of guanylate cyclase C-activating peptides guanylin and uroguanylin
Authors:JOACHIM KLODT,MICHAELA KUHN,UTE C. MARX,SILKE MARTIN,PAUL R   USCH,WOLF-GEORG FORSSMANN,KNUT ADERMANN
Affiliation:JOACHIM KLODT,MICHAELA KUHN,UTE C. MARX,SILKE MARTIN,PAUL RÖUSCH,WOLF-GEORG FORSSMANN,KNUT ADERMANN
Abstract:Recently, the peptides guanylin and uroguanylin were identified as endogenous ligands of the membrane-bound guanylate cyclase C (GC-C) that is mainly expressed in the intestinal epithelium. In the present study, bioactive guanylin and uroguanylin have been prepared by solid-phase methodology using Fmoc/HBTU chemistry. The two disulfide bonds with relative 1/3 and 2/4 connectivity have been introduced selectively by air oxidation of thiol groups and iodine treatment of Cys(Acm) residues. Using this strategy, several sequential derivatives were prepared. Temperature-dependent HPLC characterization of the bioactive products revealed that guanylin-related peptides exist as a mixture of two compounds. The isoforms are interconverted within approximately 90 min, which prevents their separate characterization. This effect was not detected for uroguanylin-like peptides. Synthetic peptides were tested for their potential to activate GC-C in cultured human colon carcinoma cells (T84), known to express high levels of GC-C. The results obtained show that both disulfide bonds are necessary for GC-C activation. The presence of the amino-terminally neighboring residues of Cys104 for guanylin and Cys100 for uroguanylin has been found to be essential for GC-C stimulation. Unexpectedly, a hybrid peptide obtained from substitution of the central tripeptide AYA of guanylin by the tripeptide VNV of uroguanylin was not bioactive. © Munksgaard 1997.
Keywords:cGMP  disulfide  guanylate cyclase C  guanylin  uroguanylin  peptide hormone  peptide synthesis  topological isomerism   .
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