Trypsin Inhibitor Assay: Expressing, Calculating, and Standardizing Inhibitor Activity in Absolute Amounts of Trypsin Inhibited or Trypsin Inhibitors

For expressing trypsin inhibitor activity (TIA), units inhibited (TUI), inhibited, and inhibitors have been used. Although the last two are preferred, their calculations in current practices require refinement. With proposed AOCS method Ba 12a-2020, four experiments were conducted, using preparations having specific of 11,625, 12,602, 13,728, 14,926 N?-benzoyl-L-arginine ethyl ester (BAEE) units/mg protein, respectively. Experiment 1 determined relationship between absorbance at 410 nm (A410) concentration. 2 involved assaying raw heated soybeans, TIA as TUI/mg sample ?g inhibited/mg sample, determining conversion factors units. 3 resembled except for purified soybean Kunitz (KTI) Bowman-Birk (BBI). Conversion correlated highly with trypsin-specific (R2 = 0.9789). After standardizing against a reference 15,000 BAEE standardized factor 0.03 A410 (1.5 TUI) was determined. It remained consistent regardless activity, or without inhibitors, type samples. By (Experiment 3), values TUI could also be calculated, enabling expression amounts pure KTI, BBI equivalents. Furthermore, when modified half substrate concentration, concentration both 4), change modifications but mg (standardized) consistent.