(32) Assay Card

General Information
Summary SFTI-1, an acyclic permutant and a [CYS-Abu]-cyclic mutant shown to possess potent trypsin inhibitory activity.
Condition The trypsin inhibitory activity of SFTI-1 and acyclic permutant were determined as association equilibrium constants (Ka). Additionally, hydrolysis rates with bovine beta-trypsin were measured.
Result Among all three peptides, the wild SFTI-1 and the analogue with the disulfide bridge only had, within the experimental error, the same activity (the Ka values 1.1 ó10 and 9.9 ó9 M?1, respectively). Both peptides displayed unchanged inhibitory activity up to 6 h. The trypsin inhibitory activity of the analogue with the head-to-tail cycle only was 2.4-fold lower. It was also remarkably faster hydrolyzed (k = 1.1 ó?4 molpeptide ólenzyme?1 ó1) upon the incubation with the enzyme than the other two peptides. This indicates that the head-to-tail cyclization is significantly less important than the disulfide bridge for maintaining trypsin inhibitory activity.
AssayType Protease inhibition

References
Zablotna E, Kazmierczak K, Jaskiewicz A, Stawikowski M, Kupryszewski G, Rolka K (2002) Chemical synthesis and kinetic study of the smallest naturally occurring trypsin inhibitor SFTI-1 isolated from sunflower seeds and its analogues. Biochem Biophys Res Commun 292:855-9

Cross-references
Proteins Assayed N-SFTI-1-C
[ABA3,11]SFTI-1
SFTI-1