title: Thiolactomycin inhibits D-aspartate oxidase: a novel approach to probing the active site environment.
abstract: D-Aspartate oxidase (DDO) and D-amino acid oxidase (DAO) are flavin adenine dinucleotide (FAD)-containing flavoproteins that catalyze the oxidative deamination of D-amino acids. While several functionally and structurally important amino acid residues have been identified in the DAO protein, little is known about the structure-function relationships of DDO. In the search for a potent DDO inhibitor as a novel tool for investigating its structure-function relationships, a large number of biologically active compounds of microbial origin were screened for their ability to inhibit the enzymatic activity of mouse DDO. We discovered several compounds that inhibited the activity of mouse DDO, and one of the compounds identified, thiolactomycin (TLM), was then characterized and evaluated as a novel DDO inhibitor. TLM reversibly inhibited the activity of mouse DDO with a mixed type of inhibition more efficiently than meso-tartrate and malonate, known competitive inhibitors of mammalian DDOs. The selectivity of TLM was investigated using various DDOs and DAOs, and it was found that TLM inhibits not only DDO, but also DAO. Further experiments with apoenzymes of DDO and DAO revealed that TLM is most likely to inhibit the activities of DDO and DAO by competition with both the substrate and the coenzyme, FAD. Structural models of mouse DDO/TLM complexes supported this finding. The binding mode of TLM to DDO was validated further by site-directed mutagenesis of an active site residue, Arg-237. Collectively, our findings show that TLM is a novel, active site-directed DDO inhibitor that will be useful for elucidating the molecular details of the active site environment of DDO.
authors.affiliation: Laboratory of Biomolecular Science, Department of Pharmaceutical Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Katane
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Saitoh
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Hanai
authors.forename: Masae
authors.initials: M
authors.lastname: Sekine
authors.forename: Takemitsu
authors.initials: T
authors.lastname: Furuchi
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Koyama
authors.forename: Izumi
authors.initials: I
authors.lastname: Nakagome
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tomoda
authors.forename: Shuichi
authors.initials: S
authors.lastname: Hirono
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Homma
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D020134:Catalytic Domain; D050804:D-Aspartate Oxidase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D004791:Enzyme Inhibitors; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D013379:Substrate Specificity; D013876:Thiophenes / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D013876:Thiophenes; C035068:thiolactomycin; D050804:D-Aspartate Oxidase