Abstract
Microorganisms that produce 5-methyluridine (ribothymidine) directly from purine nucleosides and thy mine were screened from our stock cultures. Of the 400 strains tested, Erwinia carotovora AJ-2992 was found to possess the most potent ability as to production of 5-methyluridine from guanosine and thymine. In the presence of intact cells of Er. carotovora AJ-2992 as the enzyme source, 222 mM 5-methyluridine was produced from 300 mM guanosine and 300 mM thymine at 60°C on 48 hr incubation. The enzymatic production of 5-methyluridine by Er. carotovora AJ-2992 was found to involve the following two successive reactions via ribose-1-phosphate as an intermediate: phosphorolysis of purine nucleosides to ribose-1-phosphate and purine bases by purine nucleoside phosphorylase, followed by condensation of ribose-1-phosphate and thymine into 5-methyluridine by pyrimidine nucleoside phosphorylase.
