Binding of brilliant red compound to lysozyme: insights into the enzyme toxicity of water-soluble aromatic chemicals.
The non-covalent interaction of brilliant red (BR) with lysozyme was investigated by the UV spectrometry, circular dichroism (CD) and isothermal titration calorimetry (ITC). The thermodynamic characterization of the interaction was performed and the assembly complexes were formed: lysozyme(BR)(17) at pH 2.03, lysozyme(BR)(15) at pH 3.25 and lysozyme(BR)(12) at pH 4.35, which corresponded to the physiological acidities. The ionic interaction induces a combination of multiple non-covalent bonds including hydrogen bond, hydrophobic interaction and van der Waals force. The two-step binding model of BR was found, in which one or two BR molecules entered the hydrophobic intracavity of lysozyme and the others bound to the hydrophilic outer surface of lysozyme. Moreover, BR binding resulted in change of the lysozyme conformation and inhibition of the lysozyme activity. The possible binding site and type of BR and the conformational transition of lysozyme were speculated and illustrated. This work provided a useful approach for study on enzyme toxicity of aromatic azo chemicals.
Chen
Fang-Fang
FF
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 200092 Shanghai, China.
Tang
Yi-Nan
YN
Wang
Shi-Long
SL
Gao
Hong-Wen
HW
D001391:Azo Compounds / Q000737:chemistry* / Q000633:toxicity; D001665:Binding Sites; D002151:Calorimetry; D002942:Circular Dichroism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D017433:Protein Structure, Secondary / Q000187:drug effects; D012867:Skin / Q000201:enzymology; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D001391:Azo Compounds; C059093:brilliant red 5SKH; D009113:Muramidase