GENE CLONING AND CHARACTERIZATION OF RECOMBINANT RIBOSE PHOSPHATE PYROPHOSPHOKINASE FROM A HYPERTHERMOPHILIC ARCHAEON

The gene encoding ribose phosphate pyrophosphokinase (Pk-RPPK) from a hyperthermophilic archaeon, Pyrococcus sp. KOD1 (Pk), was cloned, sequ enced and expressed in Escherichia coli. The recombinant Pk-RPPK (280 aa, 31,113 Da) was purified to homogeneity. The optimal temperature an d pH for the enzymatic activity are 50 degrees C and 7.0, respectively . The half-life of the enzymatic activity is 55 min at 70 degrees C. A unique characteristic of the enzyme is that it can utilize CTP and GT P as substrates In addition to ATP. It was also found that Co2+ in par ticular and Ni2+ markedly enhance the specific activity of the enzyme, as does Mg2+ in the presence of Co2+ (182 units/mg protein).