The present invention relates to an inosine-guanosine kinase which catalyzes the reaction of forming 5'-inosinic acid (5'-IMP) from inosine and adenosine triphosphate (ATP) or deoxyadenosine triphosphate (dATP) and the reaction of forming 5'-guanylic acid (5'-GMP) from guanosine and ATP or dATP.
