title: Aspartate kinase involved in 4-hydroxy-3-nitrosobenzamide biosynthesis in Streptomyces murayamaensis.
abstract: Streptomyces murayamensis carries two aspartate kinase (AK) genes: one for the biosynthesis of lysine, threonine, and methionine, and the other (nspJ) contained in the biosynthetic gene cluster for the secondary metabolite, 4-hydroxy-3-nitrosobenzamide, for catalyzing the first reaction. AKs involved in the biosynthesis of amino acids are often regulated allosterically by the end products. In the present study, we characterized NspJ to investigate whether AKs involved in secondary metabolism were also allosterically regulated. NspJ was in α2β2and (α2β2)2heterooligomeric forms, and was insensitive to all the compounds tested including lysine, threonine, and methionine. The reduction in the activity following the removal of ammonium sulfate, which induced subunit dissociation, suggests that the β subunit may be involved in stabilizing the structure of the α subunit in order to exhibit its activity. This study has provided the first example of a feedback-insensitive α2β2-type AK, which is involved in the secondary metabolism.
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Tsujimoto
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Yoshida
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Tomita
authors.affiliation: b Department of Biotechnology , Graduate School of Agricultural and Life Sciences, The University of Tokyo , Tokyo , Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohnishi
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Kuzuyama
authors.affiliation: a Biotechnology Research Center , The University of Tokyo , Tokyo , Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nishiyama
keywords: 3,4-AHBA production; aspartate kinase; feedback regulation