Mammalian d-amino acid oxidase (DAAO) plays an important role for d-serine metabolism in the brain and regulation of glutamatergic neurotransmission. In the present work, the structures in solution obtained by the methods of molecular dynamic simulation (MDS) and analyses of photoinduced electron transfer (ET) from aromatic amino acids to the excited isoalloxazine (Iso*) are described based upon our recent works, comparing among DAAO dimer, monomer, DAAO-benzoate (DAOB) complex dimer and monomer. The fluorescence lifetimes of DAAO and DAOB in the time domain of picoseconds and femtoseconds are used for the ET analyses as experimental data. The ET parameters (static dielectric constants near isoalloxazine (Iso), standard free energy gap (SFEG) between the photoproducts and reactants), ET rates, and related physical quantities (solvent reorganization energy, net electrostatic energy between the photoproducts and ionic groups in the proteins), in addition to MDS structures, are used to compare the protein structures. The structure of the DAOB dimer in solution obtained by MDS is substantially different from the crystal structure, and the structures of the two subunits are not equivalent in solution. The ET rates and related physical quantities also differ between the two subunits.
Part of the book: Amino Acid