A new inosine guanosine kinase (IGK) catalyses the synthesis of 5'-inosinic acid from inosine and ATP or from inosine and deoxyadenosine triphosphate (dATP); and the synthesis of 5'-guanylic acid from guanosine and ATP or from guanosine and dATP. The structure of the enzyme is given (454 amino acid residues); its mol.wt. is 48400. The working pH is 6.9-8.2 and working temp. 25-40 deg.C. The enzyme is stable over the range pH 6.6-9.0 for 16 hrs. at 4 deg.C and for 15 min. at 40 deg.C and pH 7.2. It is inhibited by Co2+, Cu2+ or Zn2+ but activated by K+/Mg2+ or K+/Mn2+. Also claimed is a DNA sequence coding for the enzyme; such DNA incorporated in a suitable vector; and transformant organisms (esp. of E. coli) incorporating the vector.
