[Molecular cloning, gene expression and characterization of purine nucleoside phosphorylase from Pseudoalteromonas sp. XM2107].

OBJECTIVE

Purine nucleoside phosphorylase (PNP, EC 2.4.2.1) is an important enzyme which is applied in nucleoside medication and intermediate biosynthesis. In this paper, we aimed to obtain the PNP gene from cold-adapted marine bacterium Pseudoalteromonas sp. XM2107 and study the characteristics of enzyme for applying in nucleoside medication and intermediate biosynthesis.

METHODS

Purine nucleoside phosphorylas gene which amplified from the cold-adapted marine bacterium Pseudoalteromonas sp. XM2107 genome by homology-based PCR cloning was cloned, sequenced and expressed at E. coli BL21 (DE3) by using expression vector pET-His. The recombinant purine nucleoside phosphorylas enzyme (XmPNP) was purified by metal chelate chromatography and its several characteristics were determined completely.

RESULTS

Analysis of entire sequences of XmPNP revealed that the whole sequence is 702 bp and coded a peptide of 233 amino acids with a calculated molecular mass of 25 kDa. Compared with mesophilic counterparts, XmPNP showed a lower temperature optimum (50 degrees C). The optimal pH for inosine phosphorolysis catalyzed by XmPNP was around 7.6 at sodium phosphate buffer. XmPNP showed the highest activity toward inosine (K(m) value, 0.382 mmol/L, at 37 degrees C) and the activity decreased in the order of guanosine and adenosine. Furthermore, XmPNP still expressed high catalytic activity and excellent thermalstability at ordinary temperature.

CONCLUSION

Both high catalytic activity and good thermalstability at ordinary temperature indicated that it will provide attractive candidate for prodrug activation and nucleoside medication biotransformation.