title: Enzymatic production of γ-aminobutyric acid in soybeans using high hydrostatic pressure and precursor feeding.
abstract: The effects were investigated of the glutamic acid (Glu) substrate concentration on the generation and kinetics of γ-aminobutyric acid (GABA) in soybeans treated under high hydrostatic pressure (HHP; 200 MPa for 10 min at 25 °C). The conversion of Glu to GABA decreased with increasing initial Glu concentration in the soybeans. The crude glutamate decarboxylase (GAD) obtained from the HHP-treated soybeans showed substrate inhibition. The GABA production rate in the HHP-treated soybeans fitted the following substrate inhibition kinetic equation: v0=(VmaxS0)/(Km+S0+(S0)2/Ki). The Km value for the HHP-treated soybeans was significantly higher than that of the untreated soybeans. The Km values in this study show the affinity between Glu and GAD, and indicate that the HHP-treated soybeans had lower affinity between Glu and GAD than the untreated soybeans. GAD extracted from the HHP-treated soybeans showed a similar value to that in the HHP-treated soybeans. The intact biochemical system was so damaged in the HHP-treated soybeans that it showed substrate inhibition kinetics similar to that of the extracted GAD. The combination of HHP and precursor feeding proved to be a novel tool that can be used to increase the concentration of a target component.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai, Japan. shigeakiu@hotmail.com
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Ueno
authors.forename: Takumi
authors.initials: T
authors.lastname: Katayama
authors.forename: Takae
authors.initials: T
authors.lastname: Watanabe
authors.forename: Kanako
authors.initials: K
authors.lastname: Nakajima
authors.forename: Mayumi
authors.initials: M
authors.lastname: Hayashi
authors.forename: Toru
authors.initials: T
authors.lastname: Shigematsu
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Fujii
mesh_terms: D001711:Biotransformation; D005511:Food Handling / Q000379:methods*; D055951:Functional Food; D005968:Glutamate Decarboxylase / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006874:Hydrostatic Pressure; D007700:Kinetics; D013025:Glycine max / Q000378:metabolism*; D014867:Water / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis*
chemical_list: D014867:Water; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase