期刊
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
卷 70, 期 19, 页码 5869-5878出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jafc.2c01796
关键词
soy sauce; prolyl endopeptidase; Aspergillus niger; Aspergillus oryzae; soybean protein
资金
- National Natural Science Foundation of China [31801537, 31801599]
- China Postdoctoral Science Foundation [2016M600380]
- Special Fund for Science and Technology Development of Zhongshan, China [2018A1007]
- Science and Technology Innovation Strategy Special Project of Yangxi, China [SDZX2021030]
This study isolated and identified an APE from Aspergillus niger that can degrade approximately 50% of the B3 subunit and increase proline content in soy sauce. APE is an acidic salt-tolerant serine protease that is optimally active at 40 degrees C and pH 4.0. High salinity affects the spatial structures and catalytic activity of APE, as well as the rigidity of the B3 subunit.
Soy sauce secondary precipitate formed due to the B3 subunit seriously affects soy sauce's appearance quality. In this study, a prolyl endopeptidase (APE) from Aspergillus niger, which could degrade approximately 50% of the B3 subunit and increase proline content by 24% in soy sauce, was isolated and identified. The results showed that APE was an acidic salt-tolerant serine protease (62 kDa), which was optimally active at 40 degrees C and pH 4.0, and retained more than 69% activity in 3 M NaCl solution over 10 days. As a potential substrate of APE, the B3 subunit contains 10 proline residues. High salinity could not damage the hydrogen bonds, salt bridges, and interior hydrophobicity of APE; thus, the spatial structures and activity of APE in 3 M NaCl solution were stable within 3 days and decreased thereafter. High salinity made the B3 subunit more rigid and lowered the catalytic activity of APE on the B3 subunit, hindering complete hydrolysis of the B3 subunit. This was the first report about the APE capable of degrading the B3 subunit and reducing the secondary precipitate of soy sauce, providing a new possibility to solve the secondary precipitate of soy sauce.
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