A general Ca-MOM platform with enhanced acid-base stability for enzyme biocatalysis

Co-precipitation of enzymes in metal-organic frameworks is a unique enzyme-immobilization strategy but is challenged by weak acid-base stability. To overcome this drawback, we discovered that Ca2+ can co-precipitate with carboxylate ligands and enzymes under ambient aqueous conditions and form enzyme@metalorganic material composites stable under a wide range of pHs (3.7-9.5). We proved this strategy on four enzymes with varied isoelectric points, molecular weights, and substrate sizes-lysozyme, lipase, glucose oxidase (GOx), and horseradish peroxidase (HRP)-as well as the cluster of HRP and GOx. Interestingly, the catalytic efficiency of the studied enzymes was found to depend on the ligand, probing the origins of which resulted in a correlation among enzyme backbone dynamics, ligand selection, and catalytic efficiency. Our approach resolved the long-lasting stability issue of aqueous-phase co-precipitation and can be generalized to bio-catalysis with other enzymes to benefit both research and industry.