Characterization of tryptic hydrolysis of alpha-lactalbumin/saponin mixture and structural change of alpha-lactalbumin interacting with soybean saponin

摘要

Bovine milk alpha-lactalbumin (alpha.-La) was mixed with soybean saponin, and the resulting mixture was hydrolyzed by trypsin. Saponin increased the tryptic-hydrolysis level of alpha-La only at relatively high phosphate buffer concentrations (greater than or equal to 0.05 M). T-1 experiments with acetylated soybean saponin demonstrated that there were some interactions between alpha-La and saponin not only at high concentrations of phosphate buffers but even at low concentrations as well. Circular dichroism spectra of alpha-La showed that the tertiary structure of alpha-La was changed through interactions with saponin only at high buffer concentrations. Furthermore, by analyzing the tryptic peptides from an alpha-La/saponin mixture, hydrolyzing rates at all or some of K5, R10, and K16 of alpha-La were accelerated by saponin interactions. The increase in the tryptic hydrolysis of of alpha-La by saponin addition was considered due to modification of the tertiary structure of alpha-La by saponin. (C) 2005 Elsevier Inc. All rights reserved.