title: Modifying the oligomeric state of cyclic amidase and its effect on enzymatic catalysis.
abstract: A group of cyclic amidases, including hydantoinase, allantoinase, dihydropyrimidinase, and dihydroorotase, catalyze the reversible hydrolysis of cyclic ureides, such as 5-monosubstituted hydantoins and dihydropyrimidines. These four enzymes carry hydrophobic patches to form dimers. With the exception of dihydroorotase, these enzymes are further dimerized to form tetramers by hydrophobic interactions. This leads us to speculate that the hydrophobic interaction domain may be a significant factor in the catalytic property of these oligomeric cyclic amidases, for which activities are not allosterically regulated. We generated a dimeric D-hydantoinase by mutating five residues in the hydrophobic alpha-helical interface of a tetramer and analyzed the kinetic properties of the dimeric form of D-hydantoinase. The specific activity of the dimeric D-hydantoinase corresponds to 5.3% of the activity of tetrameric D-hydantoinase. This low specific activity of the dimeric D-hydantoinase indicates that the dimeric interaction to form a tetramer has a significant effect on the catalytic activity of this non-allosteric tetramer.
authors.affiliation: Division of Molecular Genomic Medicine, College of Medicine, Seoul National University, Yongon-Dong, Seoul 110-799, South Korea.
authors.forename: Jongchul
authors.initials: J
authors.lastname: Yoon
authors.forename: Bora
authors.initials: B
authors.lastname: Oh
authors.forename: Kyunggon
authors.initials: K
authors.lastname: Kim
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Park
authors.forename: Jimin
authors.initials: J
authors.lastname: Wang
authors.forename: Hak-Sung
authors.initials: HS
authors.lastname: Kim
authors.forename: Youngsoo
authors.initials: Y
authors.lastname: Kim
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D002384:Catalysis; D019281:Dimerization; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008970:Molecular Weight; D016296:Mutagenesis; D017433:Protein Structure, Secondary
chemical_list: D000596:Amino Acids; D000581:Amidohydrolases; C020047:dihydropyrimidinase