STRUCTURE-ACTIVITY STUDIES ON C-TERMINAL HIRUDIN PEPTIDES CONTAINING SULFATED TYROSINE RESIDUES

To clarify the role of the negative charge of the C-terminal region of hirudin, we chemically synthesized the C-terminal peptide of hirudin variant-1 (HV-1), HV-1-(54-65), and its analogs, [E61Y,E62Y]HV-1-(54-6 5) and [E62Y]HV-1-(54-65), and then sulfated the Tyr residue(s) in the se peptides by both enzymic and chemical methods. Enzymic O-sulfation of Tyr residues in the peptides by use of sulfotransferase isolated fr om Eubacterium A-44 allowed us to produce four kinds of the sulfated p eptide, whose C-terminal sequences were -PEY(SO3H)YLQ, -PYY(SO3H)YLQ, -PYYY(SO3H)LQ and -PYY(SO3H)Y(SO3H)LQ. On the other hand, all Tyr resi dues in the peptides were successfully sulfated by chemical reaction w ith N,N-dicyclohexylcarbodiimide in the presence of sulfuric acid. Bas ed on the analysis of structure-activity relationships of these sulfat ed peptides for thrombin inhibition, the Tyr62 and Tyr63 bisulfated pe ptide GDFEEIPEY(SO3H)Y(SO3H)LQ was found to be the most potent inhibit or of thrombin among the products tested. No increase in potency was o bserved by further substitution of Glu61 with Tyr(SO3H). The inhibitor y activity by substitution with Tyr(SO3H) at position 63 was greater t han that obtained by the substitution at position 62. (C) Munksgaard 1 996.