An effective metallohydrolase model with a supramolecular environment: structures, properties, and activities.
A supramolecular inclusion complex, [Zn(L1)(H2O)2(beta-CD)](ClO4)2.9.5 H2O (1) was synthesized and characterized structurally and its first-order active species for hydrolysis of esters, [Zn(L1)(H2O)(OH)(beta-CD)](ClO4) (2), was isolated (L1=4-(4'-tert-butylbenzyl)diethylenetriamine; beta-CD=beta-cyclodextrin). The apparent inclusion stability constant of the host and the guest measured in aqueous solution was (5.91+/-0.03)x10(3) for 1. The measured values of the first- and second-order pK(a) values of coordinated water molecules were 8.20+/-0.08 and 10.44+/-0.08, respectively, and were assigned to water molecules occupying the plane and remaining axial positions in a distorted trigonal bipyramid of the [Zn(L1)(H2O)2(beta-CD)]2+ sphere according to the structural analysis of [Zn(L2)(H2O)}2(mu-OH)](ClO4)3 (3) (L2=4-benzyldiethylenetriamine). p-Nitrophenyl acetate (pNA) hydrolysis catalyzed by 1 at pH 7.5-9.1 and 25.0+/-0.1 degrees C exhibited a first-order reaction with various concentrations of pNA and 1, but the pH profile did not indicate saturated kinetic behavior. Second-order rate constants of 0.59 and 24.0 M(-1) s(-1) were calculated for [Zn(L1)(H2O)(OH)(beta-CD)]+ and [Zn(L1)(OH)2(beta-CD)], respectively; the latter exhibited a potent catalytic activity relative to the reported mononuclear and polynuclear Zn(II) species.
Zhou
Ying-Hua
YH
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (People's Republic of China).
Fu
Heng
H
Zhao
Wei-Xi
WX
Tong
Ming-Liang
ML
Su
Cheng-Yong
CY
Sun
Hongzhe
H
Ji
Liang-Nian
LN
Mao
Zong-Wan
ZW
D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D006868:Hydrolysis; D007700:Kinetics; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D018716:Molecular Mimicry; D015394:Molecular Structure; D009596:Nitrophenols / Q000378:metabolism; D010084:Oxidation-Reduction; D011199:Potentiometry; D014867:Water / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry* / Q000378:metabolism; D047392:beta-Cyclodextrins / Q000737:chemistry* / Q000378:metabolism
D009596:Nitrophenols; D017967:Zinc Compounds; D047392:beta-Cyclodextrins; D014867:Water; C008642:4-nitrophenyl acetate; D008666:Metalloendopeptidases