Heterologous Expression and Biological Characterization of Salmonella Phage PSDA-2 Depolymerase Dpo32
The gene function of phage PSDA-2 was analyzed,revealing a high sequence similarity between its tail fiber protein and the endorhamnosidase of Salmonella typhimurium,suggesting a potential polysaccharide depolymerase activity for this protein.The gene encoding the protein was cloned,heterologously expressed,and purified to obtain polysaccharide depolymerase Dpo32.The activity of the polysaccharide depolymerase was assessed using the phenol-sulfuric acid method and the double-layer agar plate method,and its stability in terms of enzyme spectrum,pH,temperature,alcohol,and metal ions was studied.The results demonstrated that Dpo32,a polysaccharide depolymerase,has the ability to enzymatically degrade Salmonella surface polysaccharides and generate reducing sugars over a broad temperature range.This enzymatic activity resulted in the lysis of one strain of Salmonella typhimurium(CICC 21483)and the formation of halos around three strains on double-layer agar plates.The results of the stability study showed that the enzyme exhibited robust activity over a wide range of conditions,including temperatures ranging from 30℃ to 80℃ and pHs from 2 to 11.Furthermore,it can maintain good activity in ionic solutions containing ≤60％alcohol and ≤10 mmol/L of K+,Ca2+,Mg2+,Cu2+,Zn2+.These findings suggest that the enzyme possesses exceptional environmental adaptability.
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