[Aim] To study the effects of single conserved amino acid residue of pyridoxine 5'-phosphate oxidase(PNPO) from Bombyx mori on its activity.[Methods] Lys111(AAA) and Ser160(AGC),two of the most conserved residues,were mutated to Glu(GAA) and Ala(GCC) by using over-lap extension,respectively.The obtained expression plasmids were over-expressed in Escherichia coli Rosetta by IPTG induction,and then the expressed products were purified with affinity chromatography and the activity of the purified PNPO were determined.[Results] The molecular mass of the target recombinant protein was ~45.0 kDa.Compared with the wild type PNPO,the activities of the mutants K111E and S160A were reduced by 78.0% and 67.4%,respectively.[Conclusion] The results suggest that the residues Lys111 and Ser160 are important to maintain the activity of PNPO.This study confirms the significance of single conserved amino acid residues on the catalytic function of PNPO of B.mori.

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The design and manufacture of SMD type dielectric ceramic duplexer used in cordless phone had been described.This duplexer contain transmission dielectric filter and receiver one. Each filter is a ceramics block, which is made of a dielectric material with high dielectric constant,high Q value and near zero temperature coefficient. The ceramics block is made up of two quarter wavelength coaxial resonators,I/O ports and coupling device.The I/O ports are postioned on lateral surface.So the filters possess compact volume ,stable structure and convenient mount. Two filters of center frequencies 903MHz and 927MHz respectly had been made by using ceramics material of dielectric constant 90,the frequency responds had been measured with Network analyzer.The result has been coincidenced with the design demand.