Effects of enzymatic deamidation by protein-glutaminase on structure and functional properties of alpha-zein.
The performance of novel protein-glutaminase (PG) purified from Chryseobacterium proteolyticumon alpha-zein was investigated. Highly insoluble alpha-zein was able to be deamidated to the extent of deamidation degree 62% by using 50 mM potassium phosphate (pH 8) containing 11.7% ethanol, at 40 degrees C for 137 h. Analysis by sodium dodecyl sulfate polyacrylamide-gel electrophoresis showed that deamidated and non-deamidated zeins have different mobilities. Results of circular dichroism spectra revealed the decline in alpha-helix contents of alpha-zein by deamidation. Besides, Fourier transform infrared spectroscopy analysis demonstrated alterations in the secondary structure of alpha-zein by deamidation. The assignment of the amide I region showed a remarkable decrease in antiparallel intermolecular beta-sheets (around 1690 cm(-1)) as an indication of the weakening aggregation ability of the deamidated molecules. Solubility and emulsification properties of alpha-zein, particularly at pH 7, were remarkably improved after the deamidation by PG. Gas chromatography and peroxide value studies pointed out that deamidated alpha-zein in powder form exhibited an inferior antioxidative property as compared with the non-deamidated one.
Yong
Yie Hui
YH
Laboratory of Quality Analysis and Assessment, Division of Agronomy and Horticultural Science, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011 Japan.
Yamaguchi
Shotaro
S
Gu
Yeun Suk
YS
Mori
Tomohiko
T
Matsumura
Yasuki
Y
D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D004655:Emulsions; D005972:Glutaminase / Q000378:metabolism*; D017433:Protein Structure, Secondary; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D015028:Zein / Q000737:chemistry* / Q000378:metabolism*
D004655:Emulsions; D015028:Zein; D005972:Glutaminase