A novel selective nucleoside phosphorylating enzyme from Morganella morganii

A selective nucleoside phosphorylating enzyme was purified to homogeneity f rom Morganella morganii NCIMB10466 crude extract. The enzyme appeared to co nsist of six subunits identical in molecular mass (M-r 25,000). It phosphor ylated various nucleosides at the 5'-position to produce nucleoside-5'-mono phosphates using pyrophosphate as the phosphate source. Energy-rich compoun ds, such as carbamylphosphate and acetylphosphate, were also very effective phosphate donors. The enzyme also exhibited phosphatase activity, and deph osphorylated various phosphate esters, but had a weak effect on nucleoside- 3'-monophosphates. Based on the results of the kinetic study, the enzyme ap peared to be an acid phosphatase. Its activity was partly inhibited by sulf hydryl reagents and heavy metal ions, but not by chelating reagents such as EDTA. Using the purified enzyme, 32.6 mM 5'-IMP was synthesized from inosi ne with a 41% molar yield, but the synthesized 5'-IMP was hydrolyzed back t o inosine and phosphate as the reaction time was extended.