title: Pivotal Enzyme in Glutamate Metabolism of Poly-g-Glutamate-Producing Microbes.
abstract: The extremely halophilic archaeon Natrialba aegyptiaca secretes the L-homo type of poly-g-glutamate (PGA) as an extremolyte. We examined the enzymes involved in glutamate metabolism and verified the presence of L-glutamate dehydrogenases, L-aspartate aminotransferase, and L-glutamate synthase. However, neither glutamate racemase nor D-amino acid aminotransferase activity was detected, suggesting the absence of sources of D-glutamate. In contrast, D-glutamate-rich PGA producers mostly possess such intracellular sources of D-glutamate. The results of our present study indicate that the D-glutamate-anabolic enzyme "glutamate racemase" is pivotal in the biosynthesis of PGA.
authors.affiliation: Graduate School of Integrated Arts and Sciences, Kochi University, Nankoku, Kochi 783-8502, Japan. ashiuchi@kochi-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ashiuchi
authors.affiliation: Graduate School of Integrated Arts and Sciences, Kochi University, Nankoku, Kochi 783-8502, Japan. b094m021@s.kochi-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Integrated Arts and Sciences, Kochi University, Nankoku, Kochi 783-8502, Japan. b094m173@s.kochi-u.ac.jp.
authors.forename: Tohru
authors.initials: T
authors.lastname: Kamei