Evaluation of the binding of UFCB and Pb-UFCB to pepsin: Spectroscopic analysis and enzyme activity assay

With ultrafine particulates (UFPs) gaining much attention by the scientific community, ultrafine carbon black (UFCB) is used as a model of UFPs, and lead is loaded on UFCB named Pb-UFCB as a model of secondary pollutants. And there are many diseases of the gastrointestinal tract whose occurrence are connected to pepsin, and the abundant physiological functions of pepsin make it highly valuable in scientific research. Meanwhile, the effects of pepsin when there are few studies on the gastrointestinal tract of UFPs on the structure, function and binding mechanism with UFCB/Pb-UFCB were researched by fluorescence spectroscopy, time-resolved fluorescence, ultraviolet-visible (UV-Vis) spectroscopy, circular dichroism (CD) and enzyme activity. The results of fluorescence quenching and time-resolved fluorescence showed UFCB can induce static quenching of pepsin, while Pb-UFCB can cause dynamic quenching. Moreover, UV-Vis and CD spectra indicated UFCB/Pb-UFCB can cause the secondary structure of pepsin changed slightly. At the same time, there was much fluctuation in the enzyme activity experiment, with the highest relative activity reaching 300% and 150%. From the results above, UFCB/Pb-UFCB have differential effects on the function and structure of pepsin. This research can be used as a supplementary material to study the interaction and influence among UFPs, heavy metals and digestive enzymes. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The research found that UFCB and Pb-UFCB have differential effects on the function and structure of pepsin, and their impact mechanisms were revealed through a variety of spectral analyses.