Production of Guanosine-5′-Monophosphate and Inosine-5′-Monophosphate by Fermentation

Abstract

Production of guanosine-5'-monophosphate and inosine-5'-monophosphate by fermentation. Appl. Microbiol. 14:821-825. 1966.-A biotin-requiring coryneform bacterium which produces glutamic acid was mutated to adenine dependency. The adenine-requiring strain, which excreted inosine-5'-monophosphate (IMP), was further mutated to xanthine dependency. As expected, IMP was also excreted by this mutant. The mutant strain was reverted to xanthine independence in an attempt to obtain a culture with an altered IMP dehydrogenase which would be less sensitive to feedback inhibition by guanosine-5'-monophosphate (GMP). A revertant was obtained which produced GMP and IMP, each at 0.5 g per liter. The reversion to xanthine independence had resulted in a concomitant requirement for isoleucine, leucine, and valine. Further mutation to increased nutritional requirements led to culture MB-1802, which accumulated 1 g per liter each of GMP and IMP. Both nucleotides were isolated in pure form. The concentrations of GMP and IMP produced by MB-1802 were four times that of cytidylate, uridylate, or adenylate, indicating that the mechanism of GMP and IMP production was direct and not via ribonucleic acid hreakdown.

Phosphohydrolases of a Bacillus subtilis Mutant Accumulating Inosine and Hypoxanthine

“…However, when de novo purine nucleotide synthesis is blocked by mutation, the products are nucleosides and free bases (1). Although we and others (8,9,20,23) have shown that Corynebacterium glutamicum mutants excrete intact 5'-nucleotides, all other microorganisms reported thus far excrete breakdown products. Purine auxotrophs of B. subtilis are of special interest because of the massive accumulations of purine intermediates generally observed with this species.…”

Genetic and Biochemical Study of Threonine-Overproducing Mutants of Saccharomyces cerevisiae

“…Another method starts with a nonfunctional mutant from which functional revertants are selected. In some cases, this second mutation simultaneously inactivates the feedback-sensitive site and restores function, originating a deregulated enzyme (5,7,23).…”