Trypsin inhibition by macrocyclic and open-chain variants of the squash inhibitor MCoTI-II

Avrutina, Olga; Schmoldt, Hans-Ulrich; Gabrijelcic-Geiger, Dusica; Le Nguyen, Dung; Sommerhoff, Christian P.; Diederichsen, Ulf und Kolmar, Harald (2005): Trypsin inhibition by macrocyclic and open-chain variants of the squash inhibitor MCoTI-II. In: Biological Chemistry, Bd. 386, Nr. 12: S. 1301-1306

Abstract

MCoTl-I and MCoTl-II from the seeds of Momordica cochinchinensis are inhibitors of trypsin-like proteases and the only known members of the large family of squash inhibitors that are cyclic and contain an additional loop connecting the amino- and the carboxy-terminus. To investigate the contribution of macrocycle formation to biological activity, we synthesized a set of open-chain variants of MCoTl-II that lack the cyclization loop and contain various natural and non-natural amino acid substitutions in the reactive-site loop. Upon replacement of P1 lysine residue \#10 within the open-chain variant of MCoTl-II by the non-natural isosteric nucleo amino acid AlaG{[}beta-(guanin-9-yl)-L-alanine], a conformationally restricted arginine mimetic, residual inhibitory activity was detected, albeit reduced by four orders of magnitude. While the cyclic inhibitors MCoTl-I and MCoTl-II were found to be very potent trypsin inhibitors, with picomolar inhibition constants, the open-chain variants displayed an approximately 10-fold lower affinity. These data suggest that the formation of a circular backbone in the MCoTI squash inhibitors results in enhanced affinity and therefore is a determinant of biological activity.

• Dokumententyp: Zeitschriftenartikel
• Publikationsform: Publisher's Version
• Fakultät: Medizin
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 1431-6730
• Allianz-/Nationallizenz: Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
• Sprache: Englisch