Nanozymatic activity of Zr-based MOFs: Tuning the coordinatively unsaturated metal sites for enhancing hydrolytic activity toward peptide bonds

Abstract

Objective: To develop efficient and stable artificial proteases and investigate the relationship between coordinatively unsaturated metal sites and hydrolysis activity of peptide bond. Methods: Three zirconium-based metal-organic frameworks （Zr-MOFs） with different coordinatively unsaturated sites （12-connected Zr-MOF, 6-connected Zr-MOF, and 4-connected Zr-MOF） were prepared to modulate protein hydrolase activity. The protein hydrolase activity of three Zr-MOFs was evaluated by the hydrolysis rate of bis-glycopeptide （Gly-Gly） as an indicator. Subsequently, soy protein, surimi protein and casein were hydrolyzed using the best performing protein hydrolase nanoenzymes, and the hydrolysis products were separated using SDS-polyacrylamide gel electrophoresis, and the hydrolysis efficiency of the three proteins by artificial proteases was investigated by staining the separated bands with Komas Brilliant Blue. Results: Among the three Zr-MOFs proteases, the 6-connected Zr-MOF showed the highest hydrolysis （52%） efficiency toward the Gly-Gly. The hydrolysis reaction rate was increased 2.63×103 times compared the uncatalyzed hydrolysis. In addition, the 6-connected Zr-MOF could respectively hydrolyze three commonly proteins in the food industry and had the highest catalytic effect on surimi protein. Conclusion: These results revealed that the ability of Zr-MOF to hydrolyze peptide bonds could be enhanced by tuning the coordinatively unsaturated sites. The study provided a new idea for the application of artificial proteases in food industry.

Keywords

• metal-organic framework
• coordinatively unsaturated sites
• nanozymes
• hydrolysis
• peptide bond