Enzymatic synthesis of vasoactive intestinal peptide analogs by transglutaminase

Vasoactive intestinal peptide is an amino acceptor and donor substrate for tissue transglutaminase (TGase) in vitro. This peptide contains a single gl utamine residue, Gln(16) which was identified as the amino acceptor substra te. Different gamma(glutamyl(16))amine derivatives of vasoactive intestinal peptide were synthesized enzymatically in vitro. The modification is very fast when compared with that of many native substrates of TGase. The analog s 1,3-diaminopropane, putrescine, cadaverine, spermidine, spermine, glycine ethyl ester and mono-dansylcadaverine of the peptide were purified by high -performance liquid chromatography on a reverse-phase column and were analy zed by electrospray mass spectrometry, When amines were absent in the assay mixture as an external amino donor, lysine residue occurring in the peptid e was an effective amino donor site for TGase. Only one of the three lysine residues of vasoactive intestinal peptide, namely Lys(21), was demonstrate d to be involved in both inter- and intramolecular cross-link formation.