title: Synthesis and biological properties of new hexapeptide substrates for vitamin K dependent carboxylase. Evidence for X-Pro cis/trans amide bond interconversions in prothrombin precursor fragment 18-23.
abstract: Three hexapeptide analogues, corresponding to sequence 18-23 of bovine prothrombin precursor [-Cys-Leu-Glu-Glu-Pro-Cys-] have been synthesized and evaluated as substrates for vitamin K dependent carboxylase. These new hexapeptides are moderately good substrates for the carboxylase but do not significantly inhibit carboxylation of Phe-Leu-Glu-Glu-Leu, a good substrate for the enzyme. Based on proton and carbon-13 NMR experiments, it is established that the conformation of sequence 18-23, which contains proline at position 22, has a trans amide bond for the Glu-Pro22 sequence in chloroform-d. This amide bond is converted to the cis amide geometry in Me2-SO-d6. It is proposed that good substrates for the carboxylase require a trans amide bond between residues 21 and 22.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015415:Biomarkers; D019735:Carbon-Carbon Ligases; D002417:Cattle; D008025:Ligases / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism*; D011498:Protein Precursors / Q000138:chemical synthesis / Q000378:metabolism*; D011516:Prothrombin / Q000138:chemical synthesis / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; D011498:Protein Precursors; C008208:acarboxyprothrombin; D011516:Prothrombin; D008025:Ligases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase