5′-Phosphodiesterase (5′-PDE) from germinated barley for hydrolysis of RNA to produce flavour nucleotides

5′-Phosphodiesterase (5′-PDE) is an enzyme that hydrolyses RNA to a mixture of ribonucleotides, from which the flavour enhancers, 5′-guanosine monophosphate (5′-GMP) and 5′-inosine monophosphate (5′-IMP) can be isolated. In the present work, 5′-PDE was extracted and partially purified from germinated barley seeds. 5′-PDE activity was monitored using bis-p-nitrophenyl phosphate as the substrate. The enzyme acts on the substrate and releases the p-nitrophenol, which is measured at 420 nm. Ultrafiltration using a polysulfone membrane having molecular weight cut off (MWCO) of 20 kDa gave 12-fold concentration. Further purification using ammonium sulphate gave 18-fold concentration. Heat shock for 15 min at 60 °C after the ultrafiltration enhanced the concentration of 5′-PDE 9.10 fold, while a similar treatment after ammonium sulphate treatment enhanced it by 17.83-fold. The enzyme had a pH optimum of 5, and was stable at 0 °C. This partially purified enzyme could be used for hydrolysis of RNA to produce 5′-GMP and 5′ adenosine monophosphate, a precursor of 5′-IMP.