ABSTRACT
Catalase is widely used in the food, medical, and textile industries. It possesses exceptional properties including high catalytic efficiency, high specificity, and environmental friendliness. Free catalase cannot be recycled and reused in industry, resulting in a costly industrial biotransformation process if catalase is used as a core ingredient. Developing a simple, mild, cost-effective, and environmentally friendly approach to immobilize catalase is anticipated to improve its utilization efficiency and enzymatic performance. In this study, the catalase KatA derived from Bacillus subtilis 168 was expressed in Escherichia coli. Following separation and purification, the purified enzyme was prepared as an immobilized enzyme in the form of enzyme-inorganic hybrid nanoflowers, and the enzymatic properties were investigated. The results indicated that the purified KatA was obtained through a three-step procedure that included ethanol precipitation, DEAE anion exchange chromatography, and hydrophobic chromatography. Then, by optimizing the process parameters, a novel KatA/Ca3(PO4)2 hybrid nanoflower was developed. The optimum reaction temperature of the free KatA was determined to be 35 ℃, the optimum reaction temperature of KatA/Ca3(PO4)2 hybrid nanoflowers was 30-35 ℃, and the optimum reaction pH of both was 11.0. The free KatA and KatA/Ca3(PO4)2 hybrid nanoflowers exhibited excellent stability at pH 4.0-11.0 and 25-50 ℃. The KatA/Ca3(PO4)2 hybrid nanoflowers demonstrated increased storage stability than that of the free KatA, maintaining 82% of the original enzymatic activity after 14 d of storage at 4 ℃, whereas the free KatA has only 50% of the original enzymatic activity. In addition, after 5 catalytic reactions, the nanoflower still maintained 55% of its initial enzymatic activity, indicating that it has good operational stability. The Km of the free KatA to the substrate hydrogen peroxide was (8.80±0.42) mmol/L, and the kcat/Km was (13 151.53± 299.19) L/(mmol·s). The Km of the KatA/Ca3(PO4)2 hybrid nanoflowers was (32.75±2.96) mmol/L, and the kcat/Km was (4 550.67±107.51) L/(mmol·s). Compared to the free KatA, the affinity of KatA/Ca3(PO4)2 hybrid nanoflowers to the substrate hydrogen peroxide was decreased, and the catalytic efficiency was also decreased. In summary, this study developed KatA/Ca3(PO4)2 hybrid nanoflowers using Ca2+ as a self-assembly inducer, which enhanced the enzymatic properties and will facilitate the environmentally friendly preparation and widespread application of immobilized catalase.
Subject(s)
Catalase , Nanostructures/chemistry , Hydrogen Peroxide/metabolism , Enzymes, Immobilized/chemistry , CatalysisABSTRACT
Objective To understand the laboratory testing current situation of ABO hemolytic disease of the newborn(ABO-HDN)in Chizhou area,and to analyze the test results of serological three indexes tests in order to provide the basis for clinical diag-nosis.Methods The ABO blood group identification and serological three indexes tests(direct antiglobulin test,free antibody test, antibody release test)were performed by using microcolumn gel method.Results A,B,O and AB blood groups were 29.13%, 31.09%,37.82% and 1.96%;the total positive rate of ABO-HDN was 22.41%(80/357),the positive rates of ABO-HDN in A and B blood groups were 38.46% (40/104)and 36.04% (40/111 )respectively;the occurrence rate of ABO-HDN had no statistical difference between blood group A and B (P >0.05);the positive rates of the direct antiglobulin test,free antibody test and antibody release test were 1.96%(7/357),4.76%(17/357)and 22.41%(80/357)respectively.Conclusion The serological three indexes tests are the main basis for the diagnosis of ABO-HDN,the antibody release test shows the highest positive rate.If clinically consid-ering HDN,the newborns should conduct the ABO-HDN screening as early as possible for clarifying the diagnosis and performing the early treatment.