Latest revision as of 17:30, 30 September 2024

AJC7/H342L-6xHis

AJC7 single point mutant

Construction

Primers were designed for the H342L point mutation, and the plasmid containing the pET-28a(+) vector was amplified using PCR. Following the mutation, the PCR products were verified by nucleic acid gel electrophoresis to confirm the presence of the desired bands. The plasmid containing the correct bands was subsequently transformed into E. coli BL21 (DE3) competent cells.

Fig.1 Point mutation localisation and primer design

Fig. 2 Nucleic acid gel plot of colony PCR

Indicator

The mutant and wild-type strains were subjected to activation and amplification culture, followed by a series of protein purification procedures to extract the target proteins, as outlined in [Experimental]. The volume of the purified enzyme solution needed for the 500 μL reaction system was determined based on the protein concentration detailed in [Experimental]. The final concentration of fructose in the reaction mixture was 100 g/L, and it included 10 μL of Ni²⁺ as a catalyst. The reaction was conducted at 70°C for 5 hours, and the resulting products were subsequently analyzed using High-Performance Liquid Chromatography (HPLC).

Result

The catalytic efficiency of the H342L mutant, when subjected to a 5-hour reaction at 70℃, showed only a slight improvement compared to the wild type under the same reaction conditions and substrate concentration.

Fig.3 The concentrations of tagose produced in the system after WT, S125D, T181A, H342L, I129T, and L140P reacted with 100 g/L substrate fructose for 5 h