An in vitro investigation of the inhibitory mechanism of beta-galactosidase by cinnamaldehyde alone and in combination with carvacrol and thymol

作者：Wang, Lang-Hong; Wang, Man-Sheng; Zeng, Xin-An^*; Gong, De-Ming; Huang, Yan-Bo

来源：Biochimica et Biophysica Acta-General Subjects, 2017, 1861(1): 3189-3198.

DOI：10.1016/j.bbagen.2016.08.002

• Cinnamaldehyde
• beta-Galactosidase
• Competitive inhibition
• Molecular modeling
• Synergistic effect

Background: Some antibacterial agents exert their antimicrobial action by targeting the cytoplasmic macromolecules, such as proteins or nucleic acids, to disturb the properties of macromolecules that may deeply influence their biological activities and functions. Cinnamaldehyde (CIN) is a natural antibacterial ingredient found in the bark and leaves of cinnamon trees.
Methods: The inhibitory mechanism of a typical enzyme, beta-galactosidase by CIN was investigated by UV-visible, fluorescence, 3-D spectroscopy, circular dichroism, atomic force microscopy and molecular modeling studies.
Results: CIN decreased the activity of beta-galactosidase by competitive inhibition through a multiphase kinetic process. 3-D spectroscopy and circular dichroism showed that the binding of CIN to beta-galactosidase resulted in changes in micro-environment of tryptophan and tyrosine residues, and conformation of beta-galactosidase. The molecular recognition was also analyzed through modeling which indicated that CIN was inserted into the active site pocket of beta-galactosidase and interacted with amino acid residues, such as Met502, Trp568, Phe601 and Trp999. Atomic force microscopy showed that a serious destabilization of the native conformation of beta-galactosidase occurred after binding with CIN, e.g., morphological changes and increased dimensions of the beta-galactosidase molecule. Moreover, it was found that the combinations of CIN, carvacrol and thymol exposure displayed synergistic effects on the inhibition of beta-galactosidase.
General significance: This study exhibits a comprehensively understanding about the action mechanism of CIN that affects the conformation and activity of beta-galactosidase in biochemical processes and provides some new insights into the possible intracellular targeting behaviors of CIN at a molecular level.

• 出版日期2017-1
• 单位华南理工大学