Fusion of the N-terminal domain of Pseudomonas sp. phytase with Bacillus sp. phytase and its effects on optimal temperature and catalytic efficiency

The beta-propeller phytase (BPP) is an enzyme that hydrolyzes phyate to release inorganic phosphorus. The BPP produced by Pseudomonas sp. FB15 (PSphy) possesses an additional N-terminal domain that is not present in BPP produced by other Bacillus species. In this study, BPP produced by Bacillus sp. SJ-10 (SJI-10phy) was fused with the N-terminal domain of PSphy and the enzymatic properties of the resulting fusion protein (FUSJ-10phy) were investigated. FUSJ-10phy exhibited an optimal temperature that was 10 degrees C lower than that of the wild-type enzyme. A comparison of kinetic parameters showed that the turnover rate of FUSJ-10phy was 2.39-fold higher than that of SJ-10phy, representing a 1.79-fold increase in catalytic efficiency. In addition, BPP produced by Bacillus sp. SJ-48 has relatively low sequence similarity with SJ-10phy, was fused with N-terminal domain (FUSJ-48phy). FUSJ-48phy also increased catalytic efficiency and changed the optimal temperature. These results indicate that, when fused to other BPPs, the N-terminal domain of PSphy increases catalytic efficiency and enzyme activity at lower temperatures.