A prodrug derivative of a bioactive peptide (or polypeptide) is provided that exhibits prolonged half-life in serum and prolonged action in vivo, compared to the parent peptide or polypeptide. In some embodiments, the peptide is selected from the group consisting of glucagon, exendin-4, GLP-1, GLP-2, GIP, vasoactive intestinal peptide (VIP), Pituitary adenylate cyclase-activating polypeptide 27 (PACAP-27), peptide histidine methionine (PHM), oxyntomodulin, secretin, osteocalcin, growth hormone releasing hormone, as well as analogs, derivatives and conjugates.