Thirty-five analogues of Phe-Leu-Glu-Glu-Leu, the pentapeptide sequence 5-9 of bovine prothrombin precursor, were synthesized and assayed as potential substrates or inhibitors of rat liver vitamin K dependent carboxylase. Carboxylation of substrate was determined by measuring the incorporation of carbon-14 labeled bicarbonate into product. Changes in substrate carboxylation produced by changing peptide chain length, amino acid chirality, ...