Expression and purification of Lysin B in mycobacteriophage D29 and analysis of its enzymatic properties
分支杆菌噬菌体D29 Lysin B的表达、纯化及酶学性质分析

LysinB(LysB)in mycobacteriophage D29 was cloned and expressed and its enzymatic properties were analysed.The lysB gene was amplified by PCR from mycobacteriophage D29 genomic DNA and inseged into pET22b vector.The constructed recombinant plasmid was transformed into Escherichia coli BL21(DE3)to express fusion protein,which was purified by Ni-NTA column and enzymatic activity detected.The results showed that expression plasmid pET22b-lysB was constructed successfully.Highly purified recombination protein(His-LysB)was obtained 33.2 mg from 1 L LB culture medium.A screenmg for His-LysB activity on esterase and lipase substrates confirmed the lipolytic activity.With p-nitrophenyl butyrate as substrate,the thermal stability of the enzyme was poor when the temperature was above 30℃.The enzyme exhibited higher stability at pH 5.0-9.5. The optimum temperature and pH for the lipolytic activity of His-LysB were 23℃ and 7.5 respectively. Under the optimum conditions, the specific activity of His-LysB was 1.3 U/mg. Zn~(2+), Cu~(2+), Mg~(2+), Mn~(2+) and phenylmethane sulfonyl fruoride severely inhibited the lipolytic activity of His-LysB. The result provides a new option for tuberculosis drug research anddevelopment.