title: Inactivation, aggregation, secondary and tertiary structural changes of germin-like protein in Satsuma mandarine with high polyphenol oxidase activity induced by ultrasonic processing.
abstract: The inhibition of Polyphenol oxidase (PPO) in plants has been widely researched for their important roles in browning reaction. A newly found germin-like protein (GLP) with high PPO activity in Satsuma mandarine was inactivated by low-frequency high-intensity ultrasonic (20 kHz) processing. The effects of ultrasound on PPO activity and structure of GLP were investigated using dynamic light scattering (DLS) analysis, transmission electron microscopy (TEM), circular dichroism (CD) spectral measurement and fluorescence spectral measurement. The lowest PPO activity achieved was 27.4% following ultrasonication for 30 min at 400 W. DLS analysis showed ultrasound caused both aggregation and dissociation of GLP particles. TEM images also demonstrated protein aggregation phenomena. CD spectra exhibited a certain number of loss in α-helix structure content. Fluorescence spectra showed remarkable increase in fluorescence intensity with tiny blue-shift following ultrasonication. In conclusion, ultrasound applied in this study induced structural changes of GLP and eventually inactivated PPO activity.
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, Wuhan, 430070, China.
authors.forename: Nana
authors.initials: N
authors.lastname: Huang
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, Wuhan, 430070, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Cheng
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, Wuhan, 430070, China. Electronic address: wanfenghu@mail.hzau.edu.cn.
authors.forename: Wanfeng
authors.initials: W
authors.lastname: Hu
authors.affiliation: College of Food Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; Key Laboratory of Environment Correlative Dietology (Huazhong Agricultural University), Ministry of Education, Wuhan, 430070, China.
authors.forename: Siyi
authors.initials: S
authors.lastname: Pan
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D002957:Citrus / Q000737:chemistry / Q000201:enzymology*; D004789:Enzyme Activation; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D066329:Protein Aggregates; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013010:Sonication
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; D066329:Protein Aggregates; C058814:germin; D004156:Catechol Oxidase
keywords: Aggregation; Germin-like protein; PPO activity; Ultrasound; structural change