Non-competitive inhibition of Ag(I) catalysis by coenzyme A: A novel strategy for detecting histone acetyltransferase activity in gastric cancer circulating tumor cells

This study introduces a novel method for detecting histone acetyltransferase (HAT) activity in gastric cancer circulating tumor cells (CTCs) by leveraging coenzyme A (CoA)-mediated non-competitive inhibition of silver ion (Ag(I)) catalysis. The interactions between CoA, Ag(I), and the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) were thoroughly examined, leading to the development of a highly sensitive and specific assay for HAT detection. Notably, this method utilizes Ag(I) to catalyze the oxidation of TMB without the need for H₂O₂, simplifying the reaction system. Our results show that CoA effectively inhibits the catalytic activity of Ag(I) in a non-competitive fashion, offering a robust means to quantify HAT activity in CTCs. By utilizing UV-Vis spectroscopy and a smartphone-based RGB platform, this method exhibited remarkable selectivity and sensitivity, with a detection limit of 0.033 ng/mL (S/N = 3). Comprehensive analysis across various cell types, including normal cells, gastric cancer cells, and simulative CTCs, revealed that HAT activity was highest in CTCs, underscoring their critical role to some extent in tumor metastasis. Furthermore, stimulation with epidermal growth factor (EGF) and tumor necrosis factor-α (TNF-α) demonstrated distinct HAT activity patterns in different cells, highlighting their differential responses to growth and inflammatory signals. This method can also be adapted to other biosensing platforms by altering metal ions and inhibitory components, showcasing its versatility and potential for real-world applications in cancer diagnostics and metastasis monitoring.