title: Isolation of cathepsin B from the muscle of silver carp (Hypophthalmichthys molitrix) and comparison of cathepsins B and L actions on surimi gel softening.
abstract: Cathepsin B from silver carp muscle was purified to 263-fold by acid treatment, ammonium sulfate fractionation, followed by a series of chromatographic separations. The molecular mass of the purified enzyme was 29kDa as determined by SDS-PAGE and immunoblotting. The purified enzyme was activated by dithiothreitol and cysteine while it was substantially inhibited by E-64, suggesting the purified enzyme belongs to the cysteine proteinase family. Optimal pH and temperature were 5.5 and 35°C, respectively. The enzyme catalyzed the hydrolysis of Z-Arg-Arg-MCA with a parameter of Km (90μM) and Kcat (20.3s(-1)), but hardly hydrolyzed Arg-MCA. Analysis of surimi gel strength and microstructure showed that cathepsins B and L were capable of destroying the network structure of silver carp surimi gels, consequently causing gel softening. Cathepsin L might play an important role in the modori effect.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, P.O. Box 303, 17, Qinghua East Road, Haidian, Beijing 100083, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, P.O. Box 303, 17, Qinghua East Road, Haidian, Beijing 100083, China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Yin
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, P.O. Box 303, 17, Qinghua East Road, Haidian, Beijing 100083, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, P.O. Box 303, 17, Qinghua East Road, Haidian, Beijing 100083, China.
authors.forename: Shuhong
authors.initials: S
authors.lastname: Li
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, P.O. Box 303, 17, Qinghua East Road, Haidian, Beijing 100083, China. Electronic address: chwma@cau.edu.cn.
authors.forename: Changwei
authors.initials: C
authors.lastname: Ma
keywords: Cathepsin B; Gel softening; Purification; Silver carp; Surimi