抄録
Brevibacterium ammoniagenes ATCC 6872 accumulates 5'-GDP and -GTP, or 5'-ADP and -ATP together with GMP or AMP in nucleotide fermentation by salvage synthesis.
With cell free extract of this strain, transphosphorylating reactions of AMP or GMP were investigated.
ATP-AMP transphosphorylating enzyme (s) was partially purified to 21.7 fold with acid treatment, salting-out and column chromatography.
In ATP-AMP and ATP-GMP transphosphorylating reactins, optimal conditions were decided such as for concentrations of enzyme, of MgCl2 and of phosphate donor, pH and cell age as the enzyme sources.
Specificities of phosphate donors and acceptors were examined with both the partially purified enzymes or the sonicate. AMP and GMP were phosphorylated by ATP rapidly, but IMP and XMP were not, therefore supporting our previous finding that Brev. ammoniagenes could not accumulated IDP, ITP, XDP and XTP in IMP and XMP fermentation, respectively.
Although ATP was the best donor for both AMP and GMP phosphorylations, other nucleoside triphosphates and PRPP were used as phosphate donors.
Furthermore, phosphorylation of ADP to ATP was investigated and possible mechanisms of nucleoside di- or triphosphates synthesis in the nucleotide fermentation were discussed.
From these results, it is suggested as a possible mechanism for nucleoside di- and triphosphate accumulation by Brev. ammoniagenes, that a nucleoside monophosphate formed is phosphorylated to a nucleoside di-phosphate with ATP or other phosphate donors and then the nucleoside diphosphate is converted to a triphosphate with these phosphate donors.
