Cyclodextrin-derived mimic of glutathione peroxidase exhibiting enzymatic specificity and high catalytic efficiency.
To elucidate the relationships between molecular recognition and catalytic ability, we chose three assay systems using three different thiol substrates, glutathione (GSH), 3-carboxyl-4-nitrobenzenethiol (CNBSH), and 4-nitrobenzenethiol (NBSH), to investigate the glutathione peroxidase (GPx) activities of 2,2'-ditellurobis(2-deoxy-beta-cyclodextrin) (2-TeCD) in the presence of a variety of structurally distinct hydroperoxides (ROOH), H2O2, tert-butyl peroxide (tBuOOH), and cumene peroxide (CuOOH), as the oxidative reagent. A comparative study of the three assay systems revealed that the cyclodextrin moiety of the GPx mimic 2-TeCD endows the molecule with selectivity for ROOH and thiol substrates, and hydrophobic interactions are the most important driving forces in 2-TeCD complexation. Furthermore, in the novel NBSH assay system, 2-TeCD can catalyze the reduction of ROOH about 3.4 x 10(5) times more efficiently than diphenyl diselenide (PhSeSePh), and its second-order rate constants for thiol are similar to some of those of native GPx. This comparative study confirms that efficient binding of the substrate is essential for the catalytic ability of the GPx mimic, and that NBSH is the preferred thiol substrate of 2-TeCD among the chosen thiol substrates. Importantly, the proposed mode of action of 2-TeCD imitates the role played by several possible noncovalent interactions between enzymes and substrates in influencing catalysis and binding.
Dong
Ze-Yuan
ZY
Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130012, China.
Huang
Xin
X
Mao
Shi-Zhong
SZ
Liang
Kai
K
Liu
Jun-Qiu
JQ
Luo
Gui-Min
GM
Shen
Jia-Cong
JC
D002384:Catalysis; D003505:Cyclodextrins / Q000737:chemistry* / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006860:Hydrogen Bonding; D006861:Hydrogen Peroxide / Q000737:chemistry; D007700:Kinetics; D018716:Molecular Mimicry; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism
D003505:Cyclodextrins; D013438:Sulfhydryl Compounds; C014712:4-nitrothiophenolate; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D005978:Glutathione