Characterization of tryptic hydrolysis of alpha-lactalbumin/saponin mixture and structural change of alpha-lactalbumin interacting with soybean saponin.
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 (> or = 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 alpha-La by saponin addition was considered due to modification of the tertiary structure of alpha-La by saponin.
Shimoyamada
Makoto
M
Laboratory of Food Material Engineering, Faculty of Agriculture, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. saponin@cc.gifu-u.ac.jp
Okada
Yuri
Y
Watanabe
Kenji
K
Yamauchi
Ryo
R
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D006868:Hydrolysis; D007768:Lactalbumin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008892:Milk / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D012503:Saponins / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin / Q000737:chemistry
D010455:Peptides; D012503:Saponins; D007768:Lactalbumin; D014357:Trypsin