Effect of sulfobetaine surfactant on the activities of bromelain and polyphenoloxidase

Abstract

To date, there is limited information regarding the interaction between zwitterionic surfactants and protein. In this study, the interaction between the sulfobetaine surfactants, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SDDAB) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SHDAB), and protein was studied by multiple techniques. Bromelain (BM) and polyphenol oxidase (PPO) were selected as model proteins. Although BM and PPO showed a very limited effect on the surface tension–concentration curve of the sulfobetaine surfactant, the sulfobetaine surfactant increased the fluorescence intensity of the enzyme, and the NMR peaks of both the surfactant and the enzyme widened obviously once they were mixed. Moreover, the sulfobetaine surfactants showed an obvious effect on the enzyme activity, and the effect of sulfobetaine surfactants on the enzyme activity was different from that of cationic and anionic surfactants. The sulfobetaine surfactants enhanced PPO activity once their concentration reached the critical micelle concentration (cmc), while they increased the BM activity obviously at a content much lower than cmc; the activity of both enzymes was eventually doubled or more. Besides, the sulfobetaine surfactants enhanced the BM activity at a broad range of temperature, pH and salt levels, while they promoted the PPO activity only at a pH lower than 8 and temperature lower than 50 °C.