The signal conversion strategy using the lytic transglycosylase Cag4-double nanoporous gold co-catalysis for the rapid screening of drugs against Helicobacter pylori infection

The cag pathogenicity island (cagPAI) is the main virulence factor of gastric carcinoma induced by Helicobacter pylori (H. pylori). The lytic transglycosylase Cag4 is an important component that assists in the translocation of the bacterial oncoprotein CagA and maintains the peptidoglycan cycle. The allosteric regulation of Cag4 has been preliminarily demonstrated to inhibit H. pylori infection. Unfortunately, a rapid screening technology for allosteric regulators of Cag4 has not been established. In this study, a novel Cag4-double nanoporous gold (NPG) biosensor based on enzyme-inorganic co-catalysis was constructed using the heterologously expressed H. pylori 26695 Cag4 as the biological recognition element for screening Cag4 allosteric regulators. The results showed that chitosan or carboxymethyl chitosan was a mixed Cag4 inhibitor combining non-competition with uncompetition. The inhibition constants were Ki' Chitosan = 0.88909 mg/mL and Ki' Carboxymethyl chitosan = 1.13480 mg/mL, respectively. Surprisingly, D-(+)-cellobiose showed the activation effect of Cag4 on E. coli MG1655 cell wall lysis by decreasing the Ka value by 29.7% and increasing the Vmax value by 71.3%. In addition, molecular docking revealed the importance of the polarity of the C2 substituent group with glucose as the main structure in the Cag4 allosteric regulator. This study provides a fast and useful platform for screening potential new drugs based on the Cag4 allosteric regulator.