Modifying the oligomeric state of cyclic amidase and its effect on enzymatic catalysis.
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.
Yoon
Jongchul
J
Division of Molecular Genomic Medicine, College of Medicine, Seoul National University, Yongon-Dong, Seoul 110-799, South Korea.
Oh
Bora
B
Kim
Kyunggon
K
Park
Jung Eun
JE
Wang
Jimin
J
Kim
Hak-Sung
HS
Kim
Youngsoo
Y
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
D000596:Amino Acids; D000581:Amidohydrolases; C020047:dihydropyrimidinase