Acta Phys. -Chim. Sin. ›› 2017, Vol. 33 ›› Issue (5): 976-983.doi: 10.3866/PKU.WHXB201702089

• ARTICLE • Previous Articles     Next Articles

Enzymatic Superactivity and Conformational Change of α-CT Induced by Cationic Gemini Surfactant

Guang-Yue BAI1,*(),Jun-Ling LIU1,Jiu-Xia WANG2,Yu-Jie WANG2,*(),Yan-Na LI1,Yang ZHAO1,*(),Mei-Huan YAO1   

  1. 1 Collaborative Innovation Centre of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, Henan Province, P. R. China
    2 School of Chemistry and Chemical Engineering, Henan Institute of Science and Technology, Xinxiang 453003, Henan Province, P. R. China
  • Received:2017-01-13 Published:2017-04-20
  • Contact: Guang-Yue BAI,Yu-Jie WANG,Yang ZHAO E-mail:baiguangyue@htu.cn;yujiewang2001@163.com;zhaoyang@htu.cn
  • Supported by:
    the National Natural Science Foundation of China(21273061);the National Natural Science Foundation of China(21573061);and Scientific Research Project of Higher Education of Henan Province, China(17A150032)

Abstract:

This work presents the correlation of the enzymatic activity of α-chymotrypsin (α-CT) with the thermodynamics of interaction between α-CT and the cationic gemini surfactant decanediyl-α, ω-bis (dodecyldimethylammonium bromide) (12-10-12). The enzymatic activity was assessed by the rate of 2-naphthyl acetate (2-NA) hydrolysis obtained from UV-Vis absorption spectra. The superactivity of α-CT in the catalytic hydrolysis of 2-NA was obtained by activation with 12-10-12 in a short incubation time; the activated α-CT showed faster denaturation kinetics. The larger superactivities appeared in a bell shape below the critical aggregation concentration (cac12-10-12, CT) of the mixed gemini/α-CT systems in buffered aqueous solution. The results obtained from the variation of the activity with the incubation time highlight that the protein incubated in 12-10-12 has a high catalysis activity and a weakened conformational stability. The mechanism of the superactivity of α-CT in the presence of 12-10-12 has been proposed by combining the results from isothermaltitration calorimetry (ITC), steady state fluorescence, and differential scanning calorimetry (DSC). The superactivity arises from perturbation of the internal structure of α-CT by an interaction between the positively charged 12-10-12 and α-CT, which makes the conformation of α-CT looser than the native one, in the balance of a weak interaction. Such a conformation is favorable for release of the acidic product of 2-NA hydrolysis, whereas it simultaneously leads to instability of the α-CT structure.

Key words: Surfactant, α-chymotrypsin, Superactivity, Isothermal titration calorimetry, Steady state fluorescence, Differential scanning calorimetry

MSC2000: 

  • O642