FIG. 4.

Synthesis of PRA from PRPP and NH₄Cl. PRA-forming activity in a cell extract from strain DM6417 was determined by using a coupled assay with GAR synthetase. In the coupled reaction a molecule of provided [¹⁴C]glycine is incorporated into the PRA structure. Synthesis of PRA from PRPP and NH₄Cl was determined as a function of [¹⁴C]GAR synthesis. Labeled GAR and glycine were separated on polyethyleneimine-cellulose with a methanol-pyridine-water (20:1:5) solvent system. Quantification determined that lane 3 contained twofold more GAR than the control lane without NH₄Cl. No increase in GAR formation was seen with cell extracts from DM6418.