Lactose inducible fermentation in Escherichia coli for improved production of recombinant urate oxidase: Optimization by statistical experimental designs

Natural polysaccharides in the prevention of hyperuricemia: Source, classification, mechanism, application in food industry

Hyperuricemia (HUA) is one of the major threats to human health. In recent years, with the gradual increase in the incidence rate of Hua, the prevention and treatment of HUA has attracted more and more attention. Clinical pharmaceutical interventions, such as Allopurinol, Febuxostat, and so on, though effective, are usually accompanied by notable adverse effects. Therefore, alternative therapy with high-safety natural components has received more and more attention from scholars. The natural polysaccharides showed a significant potential in HUA therapy and more and more natural polysaccharides for treating HUA were being obtained. Therefore, in this review, the recent progress on natural polysaccharides in preventing HUA was presented focusing on the sources, classification, and biological activities (oxidative stress, anti-inflammatory, and UA-lowering) of natural polysaccharides. Furthermore, this review explores the mechanisms of action and application. It is beneficial to the development of polysaccharides for natural HUA therapy and the results of this review could offer guidance on preventing the occurrence of HUA in daily life.

PASylated Urate Oxidase Enzyme: Enhancing Biocatalytic Activity, Physicochemical Properties, and Plasma Half-Life

Recombinant urate oxidase (UOX, E.C.1.7.3.3) is an important therapeutic enzyme used in preventing and treating chemotherapy-induced hyperuricemia and severe gout. However, UOX use is limited due to the poor stability and short plasma half-life. To solve this problem, we designed three PASylated variants of Aspergillus flavus UOX with different PAS sequences at the C- or N-terminus. The genes of native and PASylated variants (UOX-PAS₂₀, PAS₂₄-UOX, and UOX-PAS₁₀₀) were designed and produced in Escherichia coli strain BL21 (DE3). The expressed recombinant native and PASylated enzymes were compared in terms of biophysical properties, kinetics parameters, and pharmacokinetics behavior using standard methods. PASylation of UOX with PAS₁₀₀ polymer caused a 1.24-fold reduction in K _m to 52.61 μM, and a 3.87-fold increase in K _cat/K _m for uric acid compared to the native variant. UOX-PAS₁₀₀ retained its activity in different temperatures (20-55 °C); however, other variants lost nearly 50% of their original activity at 55 °C. UOX-PAS₁₀₀ exhibited a 1.78-fold increase in hydrodynamic radius and a 1.64-fold larger apparent molecular size in comparison to the native UOX. Circular dichroism (CD) spectroscopy demonstrated that the addition of the PAS tag does not change the secondary structure of the fusion enzyme. The tryptophan fluorescence emission spectra for PASylated enzymes showed a significant modification in the conformational state of UOX by the PAS polymer presence. UOX-PAS₁₀₀ retained 89.0% of the original activity following 72 h incubation in the presence of plasma at 37 °C. However, only about 61.0%, 57.0%, 50.0%, and 52.0% of activity from PAS₂₄-UOX, UOX-PAS₂₀, native UOX, and rasburicase (Fasturtec, Italy) remained, respectively, at the identical time. UOX-PAS₁₀₀ had an increased biological half-life (8.21 h) when compared with the rasburicase (3.12 h) and native UOX (2.87 h) after being injected into a rat. Having considering everything, our results suggest that the UOX-PAS₁₀₀, an A. flavus UOX fused with a C-terminally 100 amino acid PAS-residue, is a proper candidate with enhanced biological activity and extended plasma half-life for clinical therapy in patients suffering from hyperuricemia.