title: Strengthening the stability of a tunnel-shaped homotetramer protein with nanogels.
abstract: Urate oxidase (UOX, EC 1.7.3.3) is effective for the treatment of gout and hyperuricaemia associated with tumor lysis syndrome. The inherent poor stability of UOX to temperature, proteolysis, and acidic environments is known to limit its efficacy. Herein, we encapsulated UOX into spherical and porous nanogels with diameters of 20-40 nm via a two-step in situ polymerization in the presence of oxonic acid potassium salt, an inhibitor of UOX. The UOX nanogel retained 70% of the initial activity but showed an expanded pH spectrum from pH 6-10 to 3-10 and an extended half-life at 37 °C from 5 min to 3 h. The enhanced pH stability, thermal stability, and enzyme resistance of the UOX nanogels were also confirmed by using fluorescence spectroscopy and enzymatic digestion. A molecular dynamics simulation was performed as a way to probe the mechanism underlying the formation of UOX nanogels as well as the strengthened stability against harsh conditions. It was shown that the encapsulation into the polyacrylamide network reinforced the intersubunit hydrogen bonding, shielded the hydrolytic reaction site, and thus protected the tertiary and quaternary structure of UOX. The UOX nanogel with enhanced stability provided a stable enzyme model that enables the exploration of UOX in the diagnosis and therapy of disorders associated with altered purine metabolism.
authors.affiliation: Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Zhixia
authors.initials: Z
authors.lastname: Liu
authors.forename: Diannan
authors.initials: D
authors.lastname: Lu
authors.forename: Ling
authors.initials: L
authors.lastname: Yin
authors.forename: Jianmin
authors.initials: J
authors.lastname: Li
authors.forename: Yuanchen
authors.initials: Y
authors.lastname: Cui
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
mesh_terms: D002214:Capsules / Q000737:chemistry; D004355:Drug Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D056004:Molecular Dynamics Simulation; D000080385:Nanogels; D011092:Polyethylene Glycols / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry*; D014503:Urate Oxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D002214:Capsules; D000080385:Nanogels; C413692:polyethylene glycol polyethyleneimine nanogel; D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D014503:Urate Oxidase