Abstract
Picolinate binds to a reduced form of D-amino acid oxidase, and the complex formed has a broad absorption band around 600nm as in the case of the purple intermediate of the enzyme with a substrate. The dissociation constant at 25°C was 35μM at pH 7.0. The pH dependence (pH 8.3-pH 6.4) of the dissociation constant indicates that one proton is associated with the complex formation, and picolinate protonated at the N atom binds to the reduced enzyme. Resonance Raman spectra of the complex support that picolinate in the complex is a cationic form protonated at the N atom. Nicotinate also binds to the reduced enzyme, but isonicotinate does not.
