title: Nucleotides modulate the activity of aspartate racemase of Scapharca broughtonii.
abstract: The activity of D-aspartate racemase purified from Scapharca broughtonii has been found to depend markedly on some nucleotides. Purine nucleoside monophosphates enhanced the enzyme activity, which was, on the contrary, lowered by purine nucleoside triphosphates and not affected by pyrimidine nucleotides. AMP produced the highest increase of seven-fold in the enzyme activity at 6 mM and a half-maximum increase at approximately 3.8 mM. ATP caused a half-maximum decrease in the activity at approximately 1.4 mM and the remaining activity was lower than 7% at saturating ATP concentrations. AMP and ATP both brought about changes in V(max) and not in K(m). Analysis of the effect of AMP and ATP suggests that each of them has its own primary binding site, which is different from the substrate-binding site. In view of these effects of the nucleotides, the roles of the racemase and D-aspartate in energy metabolism under anoxic conditions are discussed.
authors.affiliation: Department of Environmental Systems Engineering, Nagaoka University of Technology, Niigata 940-2188, Nagaoka, Japan.
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Shibata
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Abe
authors.forename: Shouji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kera
authors.forename: Ryo-hei
authors.initials: RH
authors.lastname: Yamada
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000591:Amino Acid Isomerases / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D003445:Crustacea; D004734:Energy Metabolism; D000860:Hypoxia; D007700:Kinetics; D009711:Nucleotides / Q000494:pharmacology*
chemical_list: D009711:Nucleotides; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000591:Amino Acid Isomerases; C019749:aspartate racemase