Abstract
Excretion of intracellular 5'-inosinic acid (5'-IMP) of a series of mutants of Brevibacterium ammoniagenes selected for high 5'-IMP productivity was measured by incubating the washed cells in a phosphate buffer at 30°C. In the highest producer, KY13369, intracellular 5'-IMP was excreted partly as 5'-IMP and partly as hypoxanthine (Hx), after degradation, to the outside, which indicates the existence of two excretion systems of intracellular 5'-IMP. One is a direct excretion system of 5'-IMP and the other is an indirect excretion system coupled with degradation. 5'-IMP accumulation via the direct excretion system by the washed cells was stimulated by various energy sources and was completely inhibited by KCN, NaN3, DNPand CCCP, providing the evidence that excretion of intracellular 5'-IMP is dependent on energy-yielding reactions. The increased 5'-IMP productivity of KY13369 can be ascribed to the increased direct excretion system and to the changes of the indirect excretion system, which was more susceptible to glucose inhibition.
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