Resilient Enzymes through Immobilisation: Stable NDP Polyphosphate Phosphotransferase from Ruegeria pomeroyi for Nucleotide Regeneration

Abstract

Immobilisation plays an important role in the industrial application of enzymes. The stabilisation and reusability of immobilised enzymes reduce the cost of the catalyst and facilitate their use in continuously operated reactors. For this purpose, an applicable type of immobilisation needs to be identified. In this study, we investigate the conversion of CDP and PolyP to CTP by NDP polyphosphate phosphotransferase 3 from Ruegeria pomeroyi (RpPPK2-3) and describe the covalent immobilisation of RpPPK2-3. In order to select a suitable carrier for the immobilisation of RpPPK2-3, a screening with different amino methacrylate (glutaraldehyde-pre-activated) and epoxy methacrylate carriers was carried out. The epoxy methacrylate carrier ECR8209M (Purolite®) was found to be the most suitable. With a half-life of 462 d when stored at 6 °C and a 50-fold reusability with a 93% residual activity, the immobilised enzyme showed a higher stability compared to the soluble enzyme with a half-life of 0.04 d. Although the half-life of the soluble enzyme could be increased to 32 d by adding PPi, it could not reach the stability of the immobilisate. Due to the resilience of the immobilisate, it is suitable for application in continuous reactor set-ups, e.g., packed-bed reactors.